I always think the best relationships come out of familiarity and comfort with the individual. However in this case you are going to encounter a lot of problems from her boyfriend and your own family. The first biggest problem is that she is already taken. I don't think you want to deal with her angry boyfriend.
And even if she does break up, do you think your family will accept her? Ok..maybe you're like you know, they will be happy if they see I'm happy.
Do you think she will be as sincere with you as you are with her? Or do you think she will leave you just as readily as she left her ex?
Another thing...do you think she will become Muslim and change her lifestyle? I think it is really unfair when Muslims present themselves as average Americans and date a girl, and then at the last moment, expect the girl to renounce her religion, lifestyle and friends to conform to their social expectations. Like I=if I dated a guy expecting him to be Paki, and later he told me I would have to become Hindu , I would be really pissed off. It could be an awesome relationship but it could also cause a lot of misery....think carefully before taking any step.