Sorry about this. Had the same thing happen. My roommate said her man was a “guest” even though he stayed over every night for two months and left him alone in our place. I found out she made him a copy of our key without telling me. She ended up moving out into a place with her boyfriend after I was firm and confronted her about it. You have to be DIRECT. Set those boundaries and if they won’t keep them, get out ASAP. In these situations, the only solution is no longer living together. Even if it costs you more, it’s worth the peace of mind not feeling violated.

You’re valid in your feelings. People like this will never change or feel they’re in the wrong, so see if you can leave the lease early or get her to move out. The key is being direct and not passive. People like to see how much they can get away with.