27f With 21f Crazy Roommate

This is in NY. So I moved in with a roommate 2 months ago and ever since moving in it has been a nightmare. She has a crazy boyfriend who was banging on the house late at night and the cops were called. It was decided that he would not be welcome back in the house after this. A few weeks later I start getting threatening messages from the boyfriend. Then a few days ago I found him crawling in her bedroom window from the neighbors property and I confronted her about it (I should have called the cops then but let her parents deal with it).

Our upstairs neighbor knows this has been going on and then last night the neighbor caught the kid climbing in the window again and called the cops. 4 cops show up and hold them at the end of the street but couldn’t arrest him.

Today I called my landlord and told her about the situation and at first she was going to give the roommate 30 days notice and let me stay but then an hour later the landlord is saying something about having to evict both of us because both of our names are on the lease. Iv never heard of this before. Can anyone help?