The girl you love is in love with someone else ?

Okay , I've been talkin to this girl four about 4 months now . She has always had a girlfriend but she was fckin up . Her girlfriend HATES me with every fiberof her being, and not because I am her girls friend. So this girl is gettin played by her girlfriend ( J.M) . J.m cheats on her and lies but the girl is stuck on stupid so she turn right round and forgive . Finally they broke up and the girl was tellin me how they are reallydone and how me and her are gonna gettigether . I love this girl . I found out that J.m is happy to be single and keeps holdin on to the girl cause she hates me and knows I want hr . I'm am 99% sure about that and everybody else believes it too . I try to tell thegirl I love but she doesn't believe it even tho I bak it up time and time again. What should I do ? It's hurts too much to move on .