You need to sit her down, explain that your sister is moving in (get your sister on board with the white lie) and tell her she must leave in 2 weeks time at the latest. Also, tell her you can't afford to have her there because she doesn't pay you enough, whereas your sister will be going halves on all the bills including rent/ mortgage. Just say that you know she understands that family has to come first, therefore she MUST leave. If she doesn't come up with anything in 14 days (sharehouse/ room for rent/a flat/unit/ apartment of her own) then she will have to book an Airbnb or a hotel/motel. Do NOT let her move back into your apartment if you do get her to stay at your friends house. Leave her in your friend's house... And warn him.🚩👀 Don't give an inch past the 14 days to pack up every bit of a stuff and get it out of your property! Don't let her send her mail to your address! Good luck.