other people have already covered other aspects of this, but I’ll chime in on that last point - knowing the person or not after they transition shouldn’t really factor into it once you find out they’ve transitioned (apart from obviously having to clarify who you’re talking about to e.g. your family but in an ideal world that would be a one time thing).
I’d also add that while you will find trans people who are somewhere between ‘ok’ and ‘cool’ with using their deadname to refer to pre-transition, I think it’d be hard to find someone who would be adamant about using one name before and another name after - on the other hand it’s pretty easy to find a lot of people who will not want to be referred to in that way at all, and all things considered I would look to respect her wishes even if you no longer know her.
other people have already covered other aspects of this, but I’ll chime in on that last point - knowing the person or not after they transition shouldn’t really factor into it once you find out they’ve transitioned (apart from obviously having to clarify who you’re talking about to e.g. your family but in an ideal world that would be a one time thing).
I’d also add that while you will find trans people who are somewhere between ‘ok’ and ‘cool’ with using their deadname to refer to pre-transition, I think it’d be hard to find someone who would be adamant about using one name before and another name after - on the other hand it’s pretty easy to find a lot of people who will not want to be referred to in that way at all, and all things considered I would look to respect her wishes even if you no longer know her.