I think it would be fair and reasonable for you to say "look. This is my home and i need some space from you/her. Until further notice could you two hang out at her place, or wherever you want, unless you know i'll be gone the whole time."
Don't say it like a question. Say it like you already decided and this is how it has to be. Say it calmly and with a slightly pained expression on your face as though you banged your head on a kitchen cabinet someone left open, but didn't hurt yourself seriously, but got startled by the sudden unexpected painful bump, but you're relieved that you're not bleeding. That way it won't come across as confrontational. If you want to PM me, i'll give you my cell phone number and act out the exact tone of voice i'm trying to describe.