So I experienced this from the point of view of the person being told recently in almost the exact situation you described:
“X goes by Y and uses she/her now”
“Cool! Ask her what snacks she wants”
arrive with snacks
“Hey Y! How’s it going?”
Kor: Curzon, my beloved old friend!
Dax: I'm Jadzia now!
Kor: Jadzia, my beloved old friend!The teachings of Kahless show us that each warrior cuts their own path to Glory.
The Klingons canonically attacked and dethroned their gods so it checks out.
You're definitely overthinking this, it's totally fine to refer to her as her deadname to people who don't know and then just tell them her new name
You should ask her because maybe she doesn't want to be outed or wants to come out to those friends her own way and calling attention to the name change outs a person
public
You might be on her "best friends list" and she might have set the publicity of the post to "best friend's list only". I'd not make any dangerous assumptions about facebook working correctly or accurately conveying what you're seeing or your friend knowing how facebook works.
Same way as you'd talk about a friend from elementary school who used to be called Bobby or Davey and they go by Bob or David now.
