Have a serious problem..A girl is herrasing me to marry her.

Hi , My cousin (boy) has dated a girl for 2months. They both met in some dating app..I don't know wether had sex or not but They had a relationship for 2months but that doesn't went well.Now my cousin is not willing to marry her ,he also said to the girl its not working out...but the girl is saying that she will file a case against him...she is threatening his family a lot saying that she had contact with CI and DSP....It's affecting my cousins family mentally they are so disturbed and don't know what to do know...My cousin absconded suddenly .We are not sure what exactly we need to do on that...please suggest.. Thank you