The laws that apply to how to get someone help vary greatly from place to place.
What follows is for California:
Here in California, the "5150" law covers the "non-consenting" situation (i.e. getting someone help who does not see the need for it). The thrust of the law is that the person must be either:
1. A threat to themselves
as witnessed by a person who is listed in the law (i.e. Police Officer, Doctor, etc.)
2. A threat to someone else
as witnessed by a person who is listed in the law (i.e. Police Officer, Doctor, etc.)
In other words, bringing a relative or other loved one to a hospital or mental health facility in California and making a statement about what the person has been doing, has said, etc. won't get you anywhere (remember, this is for California). The reason for this seems to be concern for a false claim of mental illness so greedy children/relatives could benefit financially, etc. So the law here in California makes it difficult to get help for a high-functioning person who needs help but doesn't recognize the need.
Even if the person meets at least one of the above two criteria, they are only taken in for a maximum of 72 hours. If the medical professionals don't see sufficient evidence to hold the person further, they get released. Imagine the situation where you succeed in getting the person in for treatment, only to have them released and come back home to vent their feelings on you......Been there. Done that.
The agonizing thing here is that some people who don't see the need for professional help can function quite high-level, (i.e. not manifest symptoms continually), making the prospect of getting them needed assistance a minefield. I know. Been there, done that.
It is my understanding that some other states have much more enlightened statutes on this issue, for example, requiring a brief mental evaluation upon sworn statements of specific people (adult son/daughter, spouse, etc.)
I don't know enough about the situation described above and feel personally restrained from giving advice about moving out, etc. But I can understand the concern.
Nickey, hope this helps. You are not alone. As you can see, lots here in this forum have lots of love and concern to share.
---Dan