Can I file a case on my Girlfriend's father?

Hi, I am in love with a girl from different city. We talked over phone, met twice, once in a cafe and second time in a hotel. Everything thing was going normal. But last month we had some arguments, amd we stopped talking. And somehow her family got to know about our relationship. Her Father is a police sub inspector. They took her phone, one day I called on her number. Her brother picked up and abused me but I didn't say anything. Another day I sent a message, her elder brother called. And talked with me nicely. He told me that her father had threatened her that if she keeps contact with me than they will kill themselves. He tried to convince me not to call her. But I can't forget her, I don't know what to do. We belongs to same caste, but they are refusing just because I don't have a government job. I am a software engineer and I earn a lot more than what a government employee does. I also sent them my income receipt. One day called her Father, but he didn't listen anything. He threatened me to file a police case against me if I contact him or her again. I don't know what to do. I'm just 23, and never had any relation with any girl. This was my first love. And I tried but I can't forget her. It's hurting too much, I never felt this kind of pain before. I am crying for her. I stopped working now and reading. I don't do anything now. Because of her I'm losing everything. My health, my money, my education, my career everything is ruining. I always think of her and I can't stop it. I read online somewhere that I can file a case against her parents. But what will happen if she refuses in the front of the judge? She is in the pressure of her family right now. And once she told me that she can't go against her parents. They have took her phone, I can't even contact her. I don't know what she thinks and want? Can you please suggest me what should I do?