An old friend has a niece with a life-long, major mental illness. When off her medications (I've lost count of how many times, over the years), she goes "on the run", and phones home to various family members (often many times per day) with angry rants - which very often include threats of great bodily harm and/or death. Her grip on reality in that state is rather poor - asserting that Bugs Bunny and the CIA are conspiring to create a brain controlled army of polar bears with space lasers would not be unusual.

When on her medications, she is a relatively pleasant & rational person, usually able to hold an entry-level job.

Her family do not want to throw her in jail for all the threats (I'm not asserting that they could, if they wanted to), she really does not like the side effects of her medications, and (under the current system) neither confining her to a long-term mental health facility, nor reliably forcing her to take her medications seem to be available options. (Her family has talked to lawyers about their options more than once.)

What would be the "humane" thing to do? In composing your answer, please recall that her family are also humans, and - barring a premature death - she is likely to outlive most of them.

Edit: Thank you for all the replies, but my 4th-paragraph question was intended to be rhetorical. My point is that the case-by-case reality, even from the PoV of a well-to-do family that really seems to care about the mentally ill person, is often agonizingly difficult.