I don't know what to do and I hate it

hey,ok well theres this girl about 6 months ago she was going out with my best friend and she tould me that she liked me.so they broke up because of that and we didnt do anything because I couldnt do that to my best friend.so 6 months has passed and I started talking to her again and I figerd since its been so long he wouldnt care but he did but thats not even the prolbem.she has a boyfriend now but we’ve seen eachother for about 5 days now and I don’t know what to do because I like her a lot but she said she doesnt what to break up with her boyfriend. because he hasnt really done anything but we have the best time when we’re together and I dont want to lose that but I tould her just to forget me because I think I like her enough just to let her go.but yeah I just need some advice on what I should or shouldnt do.