I had to edit this, because I realized I made it seem like the only problem was guilt. But it seems to be more than that, just fear of judgment. Though I think, the pain of judgment can sometimes come from a bit of guilt and wondering what could have gone differently, even if it's small.
I hope it's OK for me to comment here as a trans person. I know this is primarily for SOs, but I think I have something I can add here that might help.
I don't think you should feel guilty. If you are not attracted to women, you are not attracted to women. Love is a lot more than sex, yeah, but for many of us, we have physical responses to one sex over the other. I know that if I was dating someone who decided to transition to male, I'd have to let them go. I know that for whatever reason, I could not give someone who is a man my full heart. We all deserve to be loved in our entirety, and sometimes, that just is not possible. In that case, the most loving thing that you can do is to give her the freedom to find someone who can give her what you cannot. It hurts for both of you. My ex recently said that she started out certain she would be OK with my transition (we broke up before I began for other reasons)...only to see me recently and feel very guilty. Because it hit her that as much as she loved me, she is no longer sure that if we were together she could have kept that conviction that our sex doesn't matter.
It happens. I've read a lot of your posts and I know you went in hoping to support Claire in every way possible, and hoping to make the relationship work. There is no doubt in my mind that you love her with all of your heart. I am certain that Claire knows how much you love her, despite the decision to split. Sometimes, things just can't last no matter how much love there may be. It's a really sad reality, but something I do not believe you should feel guilty for whatsoever.
*hug*
As peky said, you owe no one an explanation. This is between you and her, and what you think is right is all that matters in the end.