My Girl is forcing me to marry her?

I have been in a relation ship form last 10 months. And with mutual consent we had physical relation. We use to fight a lot due to compatibality issues. I asked her to wait for 4 years, but she wants its in writing. Which i denied, We had our parents meeting. Her parents doenot want a intercaste marraige and she is not ready to listen to her parents aswell. We tried to explain her that we already fight so much, there wont be a sucessful future. She doesnot want to be happy and just wants to marry me. She says i promised her and no matter what she will see to it, ' How i dont Marry her"? She has already threatened me to kill and later kill her self. He dad and mom are not really keen in her life. My parents does not want her as she has already disrespected them. I want her to be happy and move on. But she be's very reluctant and forces me to marry her. When i say 4 years for my life to be stable. She said , That is not happening. She also threatens me to take her stuff and come to my place for good. My parents explained her and asked her to leave. These all situations are making my decision strong of not marrying her. Please help!! What needs to be done in this situation? Will NC in local police station help????