Welll...sorry to break it to you, but she's taken. If there ever comes an opportunity where she's single again, I wouldn't hesitate to tell her. She's a lesbian and you know that, so it should be okay to come out with it. BUT NOT WHEN SHE'S WITH SOMEONE. Especially since she says she wants to stay committed, you should not interfere in any way. Just stay friends with her for now, because she is off limits.
Lylan