Cheating Girlfriend

Hello, I want to know if I can file a complaint against my cheating girlfriend We were in relationship for 5 and a half years. In our overall relationship we fought a lot but always patched up. May 2015 we fought over a misunderstanding and we did not spoke to each other for 5 months. Although I tried taking to her in between, but she was not interested. There are some family problems at her place, due to her brother because of which she does not want her to be a reason for more family problems. We have been quite close to each other, my whole family knew about us and she has been part of many social gathering in my family. Her family knows about me but nothing officially as she does not have guts to speak to her father. She says she does not have any problem in marrying me if her father agrees, at the same time says even if we patch up she cannot assure anything. I have messaged her father lot of times about it, but nothing concrete has come in from him. Please let me know how I can take this forward. Thanking you in advance.