Don't interfere. If she's serious with her bf, and truly loves
him, there's nothing you can do, I'm afraid. You can't make two
people break up just because you happen to like one. Sometimes it
goes beyond that. Remember, people'e emotions are at stake wherever
relationships are involved. While she's with her bf, you don't have
a chance. If she happens to break up with him, then you can tell
her how you feel about her, and maybe get somewhere. But when the
girl you like has a bf, the closest you can get is be her
friend...sorry.
if she is going to dump her current bf for you, if she meets
another guy she likes, she'll likely dump you for him
too...