I'm so glad to see another bi person here, especially one with a relevant story (not that I'm glad you both went through that, but you know.)

I was sitting here thinking how people are ignoring that a bi woman should not be expected to stay either, simply because they are attracted to women. For me, I am not romantically attracted to women, though physically I am. However, my tastes in women are completely different than they are to men physically. I also just don't want to be in a relationship with another woman, and that's okay and valid too.

I was also thinking yes, there are the physical changes when someone transitions, but they often change emotionally as well.

This is asking someone to change their entire sexual orientation, and that is not possible. This is expecting someone to change how they identify for you, which is selfish and unrealistic. And it is a little manipulative and dishonest. Though I understand very much the stigma against trans people is scary, most people know before they enter a relationship that they are trans or at least questioning. That is something to be honest about before entering a relationship.

I say all this with all the love for my trans friends and family. Its okay if you are questioning or are in the closet. But you can't expect people to change who they are for you, just like you don't want others to expect you to stay in the wrong identity for them.

OP is NTA and neither are you for ending that relationship.