Girlfriend family problems?

i met this girl 12/10/10 we started talking. so then the next 10 days i was flirting with her being super nice messeging her good morning good night complimenting her and then 12/20/10 we dated for like 3 days because of her x boyfriend sed she cheated on him with me and told me she needed to think things out. 12/30/10 we hung out at the mall i bought her a build a bear that says i love you the voice thing. and i asked her back out she said yes we hung out the next night at my friends and hada great time and kissed for the first time on the lips. it was great and we hung out yesterday 1/1/11 and it was fine she was in a bad mood already just a moody swing not pmsing or nothing. and she said we wont work cuz of my cuzon beat her up and she is scared of her they were friends so my cuz called n sed she wont touch her or anything last night but i havent talked to my gf since beefore the call and she sed to her tell him ill takl to him today so im still waiting but i dont understand i treat her perfect and other people come in and ruin it y? i believe in GOD and i preyed and cried a lot and i also have family problems already so this was just a lot more and i preyed it will get better and we can date for long and have a perfect relationship with out my couson messing things up? just right your opinion or any tips or something i need to read waht you think. i bought her sweatpants from gap aeropastale and a silver bracelet and the bear we love each other bu my couson she thinks will beat her up and do things to her so she thinks staying away from me will fix it when i want her back n my couson is trying to help me now cuz she realizes waht she did and i told her brother and my family has anger managment and hes pissed off at her and might beat the s** out of her .. right your comments tips nothing negative please thanks. this is me expressing my self so u may not even read it haha