I don't know what to do. I love this girl so much. She's the most caring, kind, and thoughtful person I know. I don't know anyone else who's as relatable and empathetic to my situation as she is. She also suffers from BPD, which I think helps her understand me better. I'm so comfortable talking to her, more so than anyone else in my life. 

The problem is that she's dating one of my friends, and he isn't too keen on dating her, but I don't think she knows. I don't want their relationship to end because I know it'll destroy her, I just want happiness for her. At the same time though, I really want to let her know how I feel. I'm stuck, I don't know what to do. Please help me.