I think I'd have to agree with what the vet said- her jaw may be permanently misaligned from either a natural defect or the previous injury.
You're correct that "loose teeth" don't hang around for long. I suppose you might check with a very experienced vet about "dental work" for a lasting solution- I'm happy to say I've never had nor heard of this problem in snakes. Since their teeth are self-replacing, I'm not sure if removing a few would help any, if it was done permanently- but ask a vet if that's an option? & do update us?