What do you do when "stans" invade your home?

I swore I wrote a comment; but I guess I didn't post it. I currently have a stan who would keep going to my sims apartment and it is starting to get annoying as they won't stay away for long. I guess you can try being mean to them if you don't mind getting a bad reputation or tell them to leave. These are either pre-made sims or sims I added into game, so I don't feel like I can just delete them.

Now one sim mine didn't even know just strolled into her apartment, played a video game on her computer then left. It is like they have no real boundaries; but luckily that only happened once, so it was probably a bug or something (as there was also a glitch when my sim tried to give an apartment key to a friend but somehow it ended up with a sim that my sim barely knew).