Ward of the state of NY living with boyfriend and boyfriends mother...?

I have a cousin, and she is 23 years old, about to be 24. She is mentally disabled, with the learning level of a 10 year old. she has made attempts at suicide, attempted to burn her mothers home down, has ran away, had unprotected sex with strangers, was caught "sexting" with other mentally disabled persons in various group homes, and is now about to move in with her mentally disabled boyfriend, with the aid of HIS mother. She has done all the financial works and has found it possible financially to move into their "own place" together... however, i am terrified that she is going to be hurt, killed or kill herself in this situation. Since she is 23, and legally an adult, and a ward of the state, her group assisted living home is allowing this union to proceed. How can i keep her safe, stop this from happening? I am not trying to be a ***** and disallow her happiness, i am being a concerned family member, who knows what she is capable of, and is trying to protect her family member... The state is NY, the county is Albany. Thank you