I agree with a few of the other comments.
1)U gave her a time limit and she's over it.
2) If she's working she should have saved enuf for rent by now
3) If it was absolute hell living in YOUR house, why is she still there?
4) If the car and u were such con's.., how come u got it thru the MOT
5) She's 29, well and truly able to act like an adult and do what most of us do and fend for herself, so why isn't she? She's decided at some point in her life to not look after herself.
6) Like most of us, give her the legally considered acceptable 1 month's notice.., 12th December and get rid of her by Xmas. If she won't go.., call police.., she hopefully will see sense and make a choice but if she doesn't.., that's her problem and CHOICE not yours.
Tell the relatives if they think its unfair, they should offer her a home. Get up and walk out of the neutral meeting place. If they hassle u, they aren't worth it. Don't make it a discussion.., its not and shouldn't be.
(Been there, put a friend of a friend up, charged no rent and he disappeared along with everything of value i owned quite literally after I complained when I asked him to do the washing up (I was working, he wasn't and didn't pay for food or anything at all.., so I learned to toughen up - oh and make sure u change the door locks).
The only people u owe anything to is your own family and yourself.