One option is to sit her down and say something along the lines of... " I know that you're in a relationship with him but i have very strong feelings for you and I'm getting the impression that you might feel the same way." Depending on her answer, you can either ask who she would prefer, him over you, or you over him. Or you could just simply tell her that you are okay with that. But whatever you do, do not confront the boyfriend because he may find you intimidating and do something he'll regret.
If you are successful in getting a girl to break up with her boyfriend for you, it is important to remember that she may leave you for someone else just as she left her previous boyfriend for you.
If she does not like her current boyfriend, another option is to wait until she breaks up with him. Then you can make your feelings known.
Remember that just because she leaves the other guy for you doesn't mean she's a cheater. To become a cheater you have to be with someone and at the same time be seeing someone behind their back.
Know that getting cheated on hurts whether you're a guy or a girl, so consider not doing anything and just let it be.
Then she has to choose you or her boyfriend.
Does the girl know you like her? How long have you an and your boyfriend been together? And are you asking what should you do?
If he is her boyfriend, hopefully, she would like him.
Try an show her how cool you are compared to her boyfriend
Treat her better than her boyfriend does.
Wait till she doesn't have a boyfriend or move on
You get beat up
Find a way to impress her.
It means that they like you more then they like there boyfriend
fight the other kid and take the girl
Move on, she's taken.
you make a girl jealous and the girl will hate her boyfriend and follow you as her boyfriend and listen to that song Justin bieber one time