Taken Money as Loan but not returning.

Hi I would like to tell the whole story so here it begins. I am student of B.com 2nd Year. I have made friendship with a girl in when we both were 1st year. After few days we have came in love relationship. After relationship started the girl asked me for 6000/- rs. as help. She assured me that she will return it in 15 days but she havent done so. As i was in relation with i havent also asked her for this. Than after few months she again asked for 2000/-, Iv helped her. Than I came to know in all this one and half year relationship, she has also done relationship with two guys. One day from facebook i have contact one of guy, he has told me the whole thing and i was shocked because she had also taken money of 1400/- from him. Now in February, 2015 when i asked her to return all the money she started to give excuse. I have given her threats if she dont return the money, i will complaint in college, but than she informed her family about all this money matter. Her older sister came and returned me 2000/- and she promised that every month we return few amounts in to your account. In May, 2015 just few days ago when I ask her family when they will return money than her mother told from 25th to 30th of every month she will deposit money on her own. But yesterday i got a call from the girl and also from her family, they asked me that "Are you still with Priya?". I have told what is the garuantee that she will not do this again. Than her family told she has changed and will be with you foreva. They also asked me to marry her but i have told to talk to my parents. I think her family dont want to return the money and want to change it in relationship. What should i do ? Kindly give me perfect advice.