I don't know for a fact but have dealt with similar situations. I think that when a person may be or is harmful to themselves where it threatens their life the doctor can speak about them to a family member. It is a fine line though and I am not for positive.
I know when my mom did try to commit suicide and ended in the hospital I was told things by the doctor and also was part of what further treatment was going to happen. I can't recall exact specifics but can share more with you if you want by pm.
If you are facing this and want a friend to I am here. I know how hard a situation like this is. Sending warm thoughts