HI--
It seems that it is time to set some boundaries with your mother. Based on her recent experiences she clearly does not understand boundaries very well--both on how people should treat her and how she should treat others. Everyone here is correct that she clearly needs help after what she's been through--but you can't force the help. A life lesson like the one she is experiencing can only be learned when a person is ready for it, and not one second before. So treat her with compassion and love, but with firm boundaries over what does and does not work for you.
As far as you know she is there for a visit because she hasn't said anything to the contrary to you. Ask her flat out how long she plans on "visiting". If she expresses a desire to stay for an extended period of time then you have the opportunity to explain to her that while you love her, you and your family are not in a position to host her for an extended stay. However, you'd be happy to assist her, in concert with your siblings, to find a place that works for her. If she does not give you a date for when her "visit" will be over then you need to pin her to one. I know she is your mother, so you feel some responsibility towards her. However, would you do this to your children? You have to treat her like the adult she is--it is the most respectful thing to do for her and yourself. If you can help her then great, but it is not your responsibility to take care of her--that is her responsibility. If she can't take care of herself then help her find a place--like a shelter--that can teach her how to take care of herself.
I'm sorry if I sound callous--it is possible to be compassionate and loving and still take care of your own needs.
Good luck!
J.