1) most women married to a man are hetero, now they're being asked to be in love and be attracted to a woman.
2) in the months or years leading to this relationship crisis, their husband has been depressed and distant and probably some anger, due to extreme discomfort, issues too, which means the relationship on rocky ground leading into it.
3) in the midst of the crisis, her partner is utterly self-absorbed. It isn't a knock, you just have to be. Often transitioners are in survival mode cause they waited too long, it's focus on their self or die. You're dealing with some intense changes and navigating dangerous waters, there is no room to consider much other than yourself.
4) ambiguous grief. as you transition, the man she fell in love with disappears and is replaced with this other person. She feels the loss, but you aren't exactly gone, so closure is impossible. The feelings linger. It's so hard on her, meanwhile you're self-absorbed
5) sex? Serious incompatibilities on both sides.
6) often the transistioner experiences a shift of some kind in their sexuality. This is a problem for both, depending on how big the shift.
Those are just the big ones I can think of, much more going on that is just completely against your relationship working out. If you look at it from her perspective, it's just too much to ask in most cases. It's not impossible because it has been done, but prepared to work very hard when you may not have the wherewithal to work on anything but yourself and still probably have it not work out.
Not trying to be a downer, just trying to show reality.
Oh PS—a split can often be the best thing for BOTH of you, even if it doesn't seem like it now.
