well....
We'd been dating for a very long time, and I was afraid of blowing it up by coming out to her.
But, it was also approaching that "commit or git" time - not imposed or suggested by her, but by me. I guess I wanted her to know before it went farther. So I told her. It freaked her out at first, although she was trying hard to reconcile it in her own mind. We did end up sitting down with my psychologist together to put all of the apprehensions and misgivings on the table and make sense of it.
She accepts me. She does still feel a little strange about it, but we've gone out a couple of times together, as ladies, and she discovered for herself that the sky didn't fall. In retrospect, what I've learned is that it was the discovering-for-herself that needed to happen for her sake. It would be easy to make this an all-about-me thing, "why can't you accept me as I am, etc", but that's not realistic or fair.
In reading this thread, I noticed that there's one singularly common theme that's been expressed, and that's guilt/depression/moodiness/pushing away over hiding and not coming out with it. Me, too. If she's the kind of person who'd love you anyway, it's only hurting her to keep it hidden. That's not an easy conclusion to reach but I think it's the right one.
And we got married in January, so I guess that's a happy ending.