I have never heard it is sinful to have short hair as a woman, but I would wholeheartedly agree that it's probably not exactly a good thing.
In this day and age, femininity is attack from all angles. It's easy for a woman to work like a man, dress like a man, wear her hair like a man, talk like the worst of men... In short, it's easy for her to totally cast off everything that she had about herself to remind herself that she is, in fact, a WOMAN, and that she needs to have the dignity and virtue a woman ought to have, and that she ought to conduct herself as a woman should. Those external reminders, I think, are not only under-appreciated today, but scorned outright as "things of the past". Dresses?! Not for me! Cooking?! You've GOT to be kidding me! Raising kids?! No way!
But look at the issue of Communion in the hand, standing. One of the biggest reasons (after that it's disrespectful to God directly to handle His sacred Body as if it were nothing but common bread) that it is wrong, is that we know external actions or signs or what have you, really and truly effect the way we believe, the way we think about things. His Excellency Bishop Fellay remarked in a talk once (in so many words), that we do not kneel to a piece of bread. We kneel to someONE... and someone who is definitely NOT equal to ourselves. But, he was saying (again in so many words), when people handle the Host as if it were nothing but bread, then it is no wonder why people end up not believing that it is anything else, and not acting as if it were anything else. And of course, to prove it, the percent of Catholics who still really, truly believe that the Host is the Body, Blood, Soul and Divinity of Christ, our Lord and our God... is scandalously low. Even though it is a principal tenant of the Catholic Faith.
I would theorize that what women have been doing... that is, how they have been living, dressing, acting, talking and so forth... can be no different. The psychology of it is exactly the same. If women cut their hair off like men, and dress in pants like men, and work like men, and try to take positions of authority like men, and talk like (again, the worst of) men, and act like men... In short, if they LIVE like men, they will indeed believe they are, and should be, no different. The problem is, this is FALSE. We ARE different. But if we remove every external reminder that could possibly help us to remember what we are and how we should behave and so on, then it is no wonder if we end up acting like men, and not only like men, but like the very worst of men, because there is something about our fallen human nature, that once a person throws off some initial restraint, they quite often end up by going totally overboard in that same direction. Thus, many women come to not only simply "choose not to" behave or dress or conduct themselves like women at all (let alone virtuous women), but they end up by having utter contempt for everything womanly to the extent of hating and scoffing at it, and finally, they not only try to become "men" (act just like men), but they very often end up being even worse (more shameless) than the men when they do. Kind of like when Moses was gone too long, the people with him didn't just turn around and leave and go back to where they came from, nor did they just appoint themselves another human leader, and have a drink on it. They threw off the authority of Moses, threw off the worship of the only true God, made themselves an idol, and did the Sodom and Gomorrah thing (got drunk and did probably every sinful thing they could do at the time).
That being said, I myself have short hair. Two reasons I keep my hair short are that 1) I have virtually no energy, let alone energy to waste taking care of it, and 2) since I've dedicated myself to God for life, I not only do not have to worry about attracting a man, but I had better hope I do NOT attract one. If it wouldn't look like lunacy (or like I was a muslem), I'd probably wear a veil or a scarf. So I won't say that there is never, ever a good reason for a woman to excuse herself. But what I will say is, all women would do very well to stop looking to excuse themselves, and instead to do as much as they can in the other direction, even if it's hard, because we need as many reminders as we can get of what we ought to be, not only in terms of womanliness, but in terms of womanly VIRTUE, as well. But out of sight, out of mind...
Once we realize that as we act, so we will believe (and the other way around, incidentally), we begin to realize that the more feminine things we women can cram into our lives, the better off we're likely to be. We need more desperately than ever to be reminded to behave ourselves as women should, and not as the world tempts us to... like immoral male slobs (not even like good men).
Frankly, I think women need to be all-out "rehabilitated" from what the world has done to most of us, and it's not something you'll get done by living like a man 24/7. We are, when all is said and done, NATURALLY WOMEN. Therefore, anything we do, or any life we live that deprives us or takes out of us that which is natural to us... to our femininity... is in a sense UNNATURAL. In that sense, you could probably argue it is also bad, if not wrong. What we need, though, is to go the other direction, back toward femininity, not to keep excusing ourselves and looking for reasons not to do it.
And if it weren't for my vow, I'd probably grow my hair down to my ankles just to spite the unholy movement (of women trying to be men).
As for men with long hair... that's a bit of a bigger question. If it turns him into a feminized dope, standing at the mirror for an hour every morning with the comb and hair spray... then no, it's probably not a good thing. But then again, even men with short hair are in danger of that vice. BUT... if the men were all throwing off their manhood en masse, so that all of them almost universally were dressing like bar-maids and talking like them, and staying at home and cooking like women, and in short trying to BE women in everything they could think of... then I would say every bit as strongly that growing their hair like women would be just another bad move for them, in a long line of other bad moves against the God-given nature of what they really are.