It is not at all clear that this lady was confused.
I'm assuming she was confused out of respect and charity to +W. If she was NOT confused then he bears MUCH MORE responsibility for not correcting her and condoning her attachment to a heretical liturgy, which will eventually erode her Faith.
You don't know what Bishop Williamson said to this lady before and after the conference.
Neither do you. All we can comment on is the public conversation.
In this video, Bishop Williamson acknowledges that he should not have made these public comments. He also acknowledges that he may not have said what he meant to say, if you listen.
That's good. +W should rightly apologize and correct the record that the new mass in an abomination and should never be attended, for any reason.
The problem is, you and Meg keep defending +W's
ORIGINAL allowance of the new mass, even when he himself has abandoned it. So both of you are at odds with +W's current view. ?? It's quite the contradiction.
If we take your example of alcohol, we can learn something applicable to this case. Alcohol is only an evil/poison when abused. St Paul tells us that "a little wine is good for the stomach",
No one in the history of Tradition has ever argued that "a little novus ordo, or a little of V2 is good for the soul".

Your analogy fails.
and of course, it is matter for the Sacrament. In counselling someone regarding alcohol intake, we need to be cognizant of certain circuмstances. You tailor the advice to the circuмstances of the individual, that is what any good physician or friend would do. The alcoholic you would advise to abstain completely, whereas your advice to others may be different. To continue the analogy, you are presuming that this lady in question is an alcoholic. You just shoot from the hip, and before you know it, you've killed someone.
The analogy is only applicable as I framed it, related to a dying alcoholic. There are no circuмstances where the new mass can be good, or nourishing, or spiritually beneficial. Go read +Ottaviani, Fr Wathen, Fr Cekada, etc.
If you believe that the new mass can be "circuмstantially" good, then you are not, and cannot be a Traditionalist. You are, by definition, part of the novus ordo church, part of the new ecuмenism, part of the conciliar revolution. The new mass was invented to lead catholics into the nєω ωσrℓ∂ σr∂єr and the coming new age, one-world religion for antichrist. Wake up before it's too late!
This lady may not be able to attend the TLM.
Maybe she is able. You don't know this. Even if she isn't able to attend the TLM, the advice to stay away from the new mass stands. No exceptions.
She may be easily able to attend a reverent New Mass offered by a certainly valid priest.
1. A reverent novus ordo is still theologically/doctrinally anti-catholic.
2. It still violates Quo Primum.
3. It is still doubtfully valid.
4. No one ordained in the new rite can be "certainly valid". That's an oxymoron.
The new mass is a theological zombie apocalypse, on top of a field of immoral land mines, all corrupted by a cloud of radioactive doctrinal heresies.
It is possible that attending this Mass, for her, would not be a danger to her faith - she may have kept the Faith for the last twenty years attending the same.
I think you have a watered-down, V2 understanding of what "keeping the Faith" means. This is your main problem.
Ceasing attendance at her local Church may be for her a danger to her Faith - we ought not to presume that we know all the circuмstances. And the Holy Eucharist is not a poison, but life-giving. "If you don't change, you are going to die" - In spite of your good intentions, you may end up killing the person you thought you were going to save. This is where pastoral prudence comes in.
See, you have a too-naturalistic view of salvation. In my case of the alcoholic, were he to quit his job, give up alcohol that very minute and die 3 days later, he might save his soul, because God would see that he ACTED to move towards morality. He took CONCRETE STEPS to change his situation, and this implies contrition for sins.
In the case of the lady, if she were to leave the bogus-ordo and heresies of V2, God would bless her IMMENSELY for her act of Faith. She may incur temporary spiritual warfare, because the devil does not want anyone to move towards the Truth, but God would not forsake her.
On the contrary, if someone "loses their faith" because they were deprived of the V2 fake-mass, one must wonder what kind of faith did they have to begin with? If a muslim finds out that Mohammed was a fraud, and "loses their faith" then we should all rejoice because this means their soul is *finally* open to the Truth of Catholicism. In the same way, if a novus ordo person "loses their faith" when deprived of the new mass, then it means they had a false faith and their spiritual "depression" will eventually lead to God enlightening them to the Truth. It's up to them to accept it.
Sometimes it takes one to hit rock bottom before God will meet them, embrace them and carry them to the heights of the Faith. Most of the novus ordo people I know are very proud and look down on the simple, unchangeable, clear teachings of the Faith. Many of them need to be humbled before they can see the childlike truths of the true Catholcism. They are too enamored with the lofty, political, protestantized V2 ideals.
I am not saying that any of these conditions are even likely. Neither is Bishop Williamson: "in certain exceptional circuмstances".
Let it be understood that this is in no way a defence of the liturgical reform, nor a downplaying of its gravity.
Heresy is heresy. Sacrilege is sacrilege. Truth is truth. Our job as catholics is to preach the truth, pure and undefiled. We cannot create exceptions, as we are not God. Jesus preached His Eucharistic mystery in John chapter 6. Most left Him that day, forever. Jesus let them walk; he did not clarify, minimize or make exceptions "in certain circuмstances". This tells us all we need to know about how God handles Truth. "
Let your yes be yes, and your no be no."
Likewise, in the context of his comments, I would like to have heard Bishop Williamson give much more emphasis to why, in general, we should shun the New Mass,
+W doesn't have time to reiterate the evils of V2 at every public meeting. Fr Wathen's book from 1971 is over 50 years old. Go read that. +W does not need to re-invent the wheel, nor does he have time to. Nor does any Trad Bishop/priest.
and I would like to hear his explanation of how and where, in 2023, we could be certain of the validity of just about any priest who says the New Mass (excluding the odd one who might have defected from the SSPX, for example...).
Certainty does not exist. All new rite priests are doubtful, so their "masses" are doubtful.
Maybe he is just presuming that his Trad audience already is fully convinced of this.
Yes, they should be.