Instead of saying "back when she was a he" or "back before [birthname] became [preferred name]" try not being a douche and say something like "before she/he came out" or "before she/he began her/his transition"! And if their transition is irrelevant to the story, say something like "when [preferred name] was a younger/in school/etc." and carry on using their current name and pronouns. Do not bring up their trans status or transition in if unnecessary! And you trying to look more interesting/cool/etc. by having a "trans friend" does not count as necessary!
