How best deal with jealous orbitors that you have to see on a daily basis that will do small things to try an pry in between you and a girl?

For example, today a guy I know that orbits one of my plates told me he hooked up with her. I’d assume it was an attempt to try and get me to stop fucking her. But when I saw her today she said “ew that’s gross.” How to deal with guys that this that you have to be around ?