How to Deal With a Douche League Guy

The harassment began when she met a guy on Tinder and he started seeing her boyfriend. She went to the cops but they couldn't do anything as there was no evidence of him or anyone else being involved. The harassment continued until I moved back with my parents who have top-notch security. After 6 years, it's all gone away except for one thing: My best friend is still ghosting me which means she got a new boyfriend under some pretext.