Roommate left 4 months ago, we got a replacement and now she wants to move back in.

The girl in question refuses to leave claiming she has every right to be here. She has not lived here since January, and has no utilities, or even a bed here. The police will not come get her, they claim she has the right to be here because she's still on the lease. The landlord knows we have a replacement, but i'm not sure if the lease has been updated or not. She's extremely hostile to everyone, and is an alcoholic. Please help

I live in Missouri