Since she's been there for months at this point, she might have a legal right to stay until she's actually been evicted. That hopefully won't be a problem since the OP said she was given notice she has to be out by this Wednesday, but if she doesn't leave then the OP or her mother will have to find out if they can legally kick her out or if they have to officially give her notice that she's being evicted and then wait however long they legally have to wait. After that they can just kick her out and change the locks and be done with her.
OP, will she be out by Wednesday as she was told she had to be?
Does the fact that OP also doesn't pay any rent, complicate things? I mean, can the OP really kick anyone out? I would assume that the OP's mother (who pays the rent) would have to do it. I suspect, given the OP's track record, nothing official (or in writing) was done.

