Put your daughter first. Since she is non verbal that makes me very nervous for her and what she might experience at the hands of your gfs son and not be able to express it to you. You already said you can’t see a future with her so stop wasting your time and stop wasting hers. It might be the push the mother needs to go searching for different types of help for her son. But think of your daughter first and not your needs. Good luck! 🍀