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Unless she is very clearly doing this to rebel and shove it in your face, if she is actively turning  her younger siblings against the Faith and against you, I would do nothing as extreme as tossing her out on her own unless you know she is able to support herself out in the world in a moral manner. Age-wise, she is an adult, has been since 18. That does not mean, however that she is an adult morally, mentally, emotionally, socially.
As for burning her clothes, taking her phone, etc, that is probably going to backfire. She will find ways to replace the clothes, the phone, etc. That may result in her leaving home as an act of rebellion and the end won’t be pretty. She’ll go more extreme, gravitate to more and worldliness and end by shacking up and carrying your grandchild.
It seems her heart is not truly converted despite her upbringing and education. I suspect she’s doing this for two reasons, 1) get your attention that’s she’s “grown up,” thinks she is because she’s 20, going on 21, which in the US is considered full adulthood. From what I see in the world, most young adults are not really mature except physically, at 21. Things have gotten worse since the c-sickness. Children, teens especially, regressed significantly since that time. 
2) I suspect your daughter is not only unconverted, no more than on a child’s level. What is sufficient for a child, does not make the grade for an adult. Look at the writings of St. Paul. Milk was great at first, but it falls short at age 20. She’s reacting to having no meat in her life. Somehow along the way, she did not learn how to function as a Catholic adult out in the world. She needs to see Catholics who are mature enough to function as faithful Catholics in the world. Often, parents do not actively teach their children by long term example how this is done. They need to see and practice for themselves applying the faith in real life, all that stuff they “learned” in school and church and family in a faithless world. If you’ve kept your daughter very sheltered, and think about it—-if she hasn’t seen her parents, friends, other family regularly interacting with people outside the tradcat ghetto, she needs to see it. How does your Faith strengthen you in the world?
There IS a time to shelter your children, but they’ll need to know how to be in the world but not of it. If there is always an emphasis on the negative, the young adult or teen will necessarily put your teachings to the test for themselves. They think, “That lady and her live-in boyfriend aren’t nasty, evil people, after all.” So why can’t I wear shorts and a skimpy top? Mr. X and Mr. Y. aren’t Catholic, and neither of them tried to force me into bed. They’re gentlemanly, respectful, have good manners. They don’t get drunk, do drugs, have baby mamas all over town. They’re into good music, not rap and the black culture crap. They’re employed, well educated, not at all like I’ve been taught. So does it really matter they aren’t traditional Catholics? And they aren’t religious at all!
Forgive me if I’m way off base in my thinking, but I would not go for any extremes here. Some suggestions are principles (Don’t say rules) of basic respect. While she is physically in your house, on your property, or with you and her siblings in public, she must wear a dress, skirt, and a top that as a minimum covers the midriff and shoulders, and may not show a cleavage crack. If she changes elsewhere or puts on a wrap skirt over the shorts and does something similar with the top, she may need only one off-color comment, gesture, or touch from some creep, to open her eyes. Tell her she is NOT a parent to her siblings and the minimum principles are for her, not her underaged siblings. If even one of them tries you out—- and they will—-they will suffer consequences. Decide in advance what they are, and carry them out.
2). Sign up for a wholesome adult activity or club open to the public, something she likes, arts and crafts, pottery, music, gardening, cooking, square-dancing, (not ballet!) taking care of animals, volunteer at a soup kitchen; somewhere she’ll interact with non-tradcats. Show her how it’s done without shedding the outward aspects. If someone asks, let her hear you give a natural, matter-of-fact response. (No sermons!) If YOU can’t do it, or are uncomfortable around non-tradcats, educate yourself first. Don’t expect it of your daughter! 
3) Require your daughter to have a paying job, a percentage of which she must give to the running of your household. If she makes enough, set aside 10% (or less) for your chapel. Even if she doesn’t attend Mass, she’s living under your roof as your daughter, not tenant or unrelated boarder. Start paying part or all of a regular bill. For example, my 20 year old nephew lives at home, works 50-60 hours, takes a course in computer generated or AI stuff related to building safety. It’s two days per week for two hours each, one remote, the other at a nearby university. He pays the fuel oil bill, to heat the house. If he doesn’t pay, the tank runs dry, and the house gets really cold in winter.  (His job is security guard at a men’s overnight shelter. No, not a suitable job for your daughter unless she’s 6’5”, lifts weights and runs long distance, can hold her own in a street fight, open carries, and is trained in taser and is certified in First Aid!) If possible, let her, when she’s 21, work outside your immediate chapel community. If need be, in the world, make sure it’s a job with little to no downtime, cashier in a busy retail outlet, a commercial print or framing shop where they’ll give her training and she’ll be busy, no time for socializing beyond a 15 minute coffee break!  You have to be on time, do your job well, no messing around. Get used to having to obey a boss the same as the sisters at school. The sisters deserve respect; a boss may be a jerk, nonetheless you toe the line or you get fired. If you’re job involves any contact with the general public, there will dress standards or an ugly smock or uniform. You suck it up and wear it. There was a time in the early 1970’s, when our house smelled of McDonalds, Duncin Donuts, Arthur Treacher’s Fish & Chips, and the perspiration of three teenagers. You really sweated in that old polyester fabric!  (Wearing a skirt and blouse at home isn’t so bad, after all!)
2) If she has only a diploma from an SSPX school, require her to be in further education. Get her GED if she doesn’t have it. If so, make sure she’s enrolled in other classes of practical use. There are a plethora of them online and at community colleges. Yes, a couple hours of free time are needed, but more than that are unhealthy for anyone. Saturday afternoon and Sunday afternoon or Sunday, at a minimum, should be set aside for family recreation.
3) If she does not already, make sure she has household and family chores for which SHE is entirely responsible. IOW, if she doesn’t do it, everybody suffers. Like, cook Wednesday dinner without reminders. Come 6:30 or whenever you eat, there’s no meal on the table, she’ll  be sure to hear about it. If Mom ends up cooking on her night off, she’s has to cook an extra dinner within a week. Let one of her chores be something physical outdoors. It’s good for the health.
4) Give her a curfew, one with the privileges of adulthood. Maybe she can come home at midnight or 1:00 am on Friday’s, except First Friday. If she takes an unpopular time, like 3-4 AM, so long as it’s safe, let her do it. Weekdays, it should be earlier unless she’s working. If you turn in before her, no sweat. Get an old-fashioned wind up alarm clock, no internet or item that can be remotely operated. Set it for her exact curfew time and place it where others cannot get at it but where you’ll wake up when it rings. Your daughter has to arrive home a few minutes before the curfew and come in your room to turn it off. If it rings, you wake up and she’s in trouble except for a really valid reason!  If it’s turned off, you sleep through, your daughter is home and all is well. Being the eldest myself, my father placed the alarm where it was too high for my siblings to access without making enough noise to wake my parents, lest I be sneaky and get one of them to turn it off. It may sound excessive for a 20 year old, but some house rules are just what they are. Fully adult people show enough respect to honor them. Phase the rule out if it’s no longer needed.
YOUR HOUSE: YOUR RULES.
If, by any chance, your daughter refuses to cooperate, maybe she could live with relatives, grandparents, cousins, another chapel family, either full time or during the week, even in another state! There are many possibilities before it comes to burning her clothes or tossing her out without ability to live responsibly on her own.
Do whatever you need to do to avoid a little no term or family estrangement. If she comes in in jeans or whatever, see, first, if she goes to change her clothes. If she does, say nothing, but give some small sign of approval. If she doesn’t, say something like, “It’s time for dinner, so we’ll wait five minutes for you.” You don’t need to say “to change clothes.” If asks for what, calmly say, “Oh, you know.” and everyone head to the table. She wants a rise from you, don’t give her the privilege. My guess is that she will mature and may adjust or move out on her own. If she’s 21, it’s really out of your hands if she goes against everything she’s been taught. Keep the same basic rules. Dress properly when you visit. If you’re shacking up, your honey bun is not permitted to come in. He stays in the car or stands outside, not on your porch, your deck or patio, or he can go somewhere else come back. When you’re a married Catholic couple, that changes.
There’s other suggestions, but this too long. Institute maybe the clothing rules for house only to start. I think she’s trying to sort things out for herself. Some people, even most, if raised well by two Catholic married parents who practice the Faith interiorly as well as exteriorly, are prodigals. They may explore a bit, test things out, but eventually come around.
Remember the joke about the 16 year old who’s dismayed his parents are really stupid. At 26, he’s amazed how much they’ve learned in one decad