My best friend and I are both female. Awhile ago we were hanging out. Just sitting on her couch watching TV, and it was quiet. Randomly she asks me if I think we should become sexually active. I turned her down of course, she's my best friend. But, I can't imagine why she would ask me. I want to discard it as a joke, but she was serious. And if she was kidding then it'd be something we laugh about now. Or something she'd laugh at then. But, there was just an awkward silence until she got a call.
Background of our friendship:
I'm bi, she's not. We're really close, and have been friends for the last 4 years. She's an affectionate person, but I never relate it to her sexuality. She calls me boo, we spoon sometimes, and like she jokes about sexual things with me, towards me a lot. Like daily. But... I still would never relate it to her sexuality. It's just the way she is. Both of our parents from biological to step parents seem to think we're more than friends. But, really it's just annoying to the both of us. She laughs it off though, because it's more of my parents than hers. And maybe because of the two times she put hickies on my neck and chest. We were wrestling, and she's hella strong for no reason.
One thing I will say is weird is how jealous she is of my other 2 close friends

As a member of the bisexual community I think that she may just want to try it out and would rather her first time be with her best friend than with some random girl. It seems like y'all are close enough to where topics like this can be brought up with out the uncomfortable feeling. You just need to talk to her about and see where she is coming from with it. Get drunk and do it is the best advice that I can give you if you aren't comfortable doing it with her sober.. hope everything works out for you!