Thanks to all of you for being so supportive! And firstofthree, thanks for the tip about giving things time.
I don't know if I really want to be sexual alone with her, not because she isn't gorgeous or anything but because we've never had even a hint of a romantic relationship. We're still quite good friends, and we care about each other, and that's why I say we feel almost like an emotional triangle - she's kind of like a sister to me and I love her to death, but not in the same way we both respectively love BF. He's definitely the hinge here, though we're not swinging wildly around, if that image makes sense haha. We're definitely connected to each other, just not through romantic, passionate love. Gawd I keep thinking of "sister wives" and shuddering, because that's kind of how we feel but that just makes me think of the show haha