Pharsi, it's really hard to answer your questions not knowing the whole situation.

"She simply said half/half. After I came back here, I again asked her what fractions of your love you offer to me, she said 50%.Was this enough for a break up or was just my mentality that she was using me to get in the us? "

Honestly, I don't think that reason was good to break up with her. It sounds like you didn't give her space. If she was seeing another guy behind your back, that would be a different story. But she was just hanging out with her friends?