What would you do if you like your bf brother...?

theres this girl thats dating a guy... they are good together... little squabbles here and there... then one day she gets invited to a family party where she meets the bf brother... they find out he have a lot of things in common... later on... they see each other more often coz bf like to hang out with bro now that he is home from college...the bf doesnt really treat her good. but bf brother knows whats she really deserves... the girl know the bf brother has feelings for her. and she now is deveping feelings for him.. what shoud she do or they do abut the situation...