Im not sure why it is she has to stay with you but now its been decided she's staying for the forseeable future some boundaries definately have to be laid down. Could you get your partner to talk to her if she's just not listening to you? i wouldn't dare be so messy and inconsiderate in someone else's house but clearly she's not so self-conscious. If your partner is uneasy about talking to her than that only really leaves you to try and resolve the situation - even if he too has a problem with her behaviour. Perhaps if you sit down with her over a cup of coffee (maybe you could convince your partner to join you?) and explain that some things simply need to change the penny might drop once and for all. The DBT technique 'GIVE' states that if you use a Gentle, Interested, Validating and an Easy manner you're more likey to get what you want. Maybe start by asking whether she's comfortable and if theres anything she would like to talk about? i know this sounds pretty tough - especially if she's been taking advantage as much as you say but at least if you've tried approaching the situation diplomatically at first you'll feel better that you did your best to resolve the situation if things do deteriorate from there. I wish you all the best.