I'm all to familiar with your situation.
I have a sister that has mental issues. Several years ago I tried to help her. Brought her into my home, got her therapy, medical help, got her on SSI disability etc. She lived with me and the wife for 1 1/2 years. Got her on her feet with her own apartment. Wife and I went out of town for our anniversary for 10 days. Got back to find out she had let herself in my house, through a party, did damage to my house and, during the party, someone stole all my wife's jewelry. A lifetime of collecting along with jewelry her mother, grandmother and great grandmother had given her. I haven't laid eyes on the sister since about a month before that happened. Last I heard she was living in a tent behind a strip mall. I could care less.