The therapist is legally bound to confidentiality, not the client, so I think this is really strange behavior on the part of your T and she handled it very poorly. Your therapist cannot talk to clients about other clients, so unfortunately her hands were tied in that regard. However, it was her responsibility to make that clear and not engage in discussion about it. That doesn't make it easier for you so I imagine from that point on it would have been difficult for her to remain your T. Still, it should have been addressed more skillfully and she should have tried in some way to make it work for you. I think you could consider this abandonment, simply because she handled it so poorly. I don't know that it would hold up in a complaint, but philosophically I agree with your perception of it.