DIL... providing food and shelter is a grey area for many of us, and I AM getting mixed viewpoints on this. Just last night in my group therapy, two parents said that they had gone to the grocery store and purchased for their daughter a few items which they considered to be the "bare necessities." The counselor said he didn't see anything wrong with this.
An idea that comes to my mind for you to try... find out the address and phone number of the nearest shelter and soup kitchen (like Salvation Army, or something). Give this information to your AMIL. This way, you are helping her, but you are not "doing" for her. You MIL may slowly come to the realization that things in her life have become out of control.