MRT, I think that is really awful. I would also be very upset and devastated I think in your position.
Of course I don't think it is absolutely always awful and devastating for a therapist to accept a promotion that involves moving away. But if they know that there is any chance at all that at some point in their career, before retirement, they might apply for another job, they should NOT promise the contrary. That's so damaging and the opposite of helping with attachment problems, it must have reinforced your negative experience that anyone who is important or claims to be trustworthy will leave. I think your T handled things badly and should have been a lot more careful with your feelings i.e. not making promises she could not keep. I'm really sorry that happened