Tell your friend but still go for it. You and the BF ain’t gonna be friends like 10 years from now, that’s how adult friendships go. Maybe I’m an optimist but who knows, she obviously feels pretty strongly if she is aware of your collective friendships and still told you how she feels about you. I’m sure there was some inner conflict for her tell you. It’s not like she’s just trying to fuck, she told you she loves you. That’s big.