My girlfriend cheated me after their family fixed another alliance ?

Me and my girlfriend was in relationship from 2016 Jan till April 29 2024 On this day April 29 she was talking to me very fine like “I don’t want to miss you “ and “I need you” in the evening and in the night I said it’s my own Sister’s birthday so I would be busy, Immediately she started to show the hate through the text messages and broke up with me. Then later one week I texted her again and she said “I’m not expecting your message so leave” It’s almost 8 years we have been in love we had huge fights and we patchup very soon but this time It hit very different Her family got an alliance for her and she accepted and moved on and I here still waiting she would come back to me after her anger chills down. Nobody was ready to inform and her parents are not ready to talk to me and they are eager to get her married to another person My question is if she didn’t wanted to marry me then why did she gave a fake hope of marrying me and had sex with me Why to use the name of love for just sex? I have the proofs of WhatsApp and Instagram texts where she gave me a hope of marrying me promised me. Our photos together in the OYO. I want to file a complaint on her What should I do ?