Should I wait for the girl I love?

Ok it sounds like you only have one chance at this relationship. All you can do for now is wait until she breaks up with her current boyfriend. You don't want to give her the notion (like you said) to leave her boyfriend for you. When she does leave her current boyfriend go up to her and tell her how you feel about her. Tell her you've been good friends since whenever and that you enjoy every moment of being with her. Hopefully she will love the idea because everyone has feelings for his/her best boy/girl friend at least once or at least thought about it. Just play it cool and you'll be fine. Hope this helped.