Oh, I'm glad you read (and liked) Taking Care of Terrific! "A subversive book" is a really good way to put it (and it's interesting that the locations are still recognizable 40 years on).
I never thought about the idea of wanting to change your name being treated as a phase; I think I always thought of the last scene as being less about her name per se and more about feeling happier with being who she is in general, but it's an interesting point that "learning to love who you are" (as the book parodies midway through) gets more complicated with issues of trans representation, etc.
(Also, come to think of it I first read it thirty years ago and I still don't know whether Enid is pronounced en-id or ee-nid.)