Friend’s partner is a danger to himself and others, threatened to end others or himself if cops are called. Can I legally keep her in 5150 with evidence? Also evict?

This has been going on since August and I barely found out now how bad it has gotten. The partner yells and forces my friend to solely hang out with them only. Doesn’t let her be with others. If I text her, he tells her not to read them. Isolates her from friends. And it has gotten to him verbally threatening harming anyone they deem as “evil”, which is almost everyone.

Christmas they threatened to off anyone who called the police on them or off themselves.

For context, they have been to the ward in the past in 2019 for a suicide attempt. Now they won’t make efforts to go get their medications, won’t set doctors appointments, refuse therapy, and has been abusing my friend these past few months.

My friend flew to Michigan where he lived in 2022. They both mutually agreed to move back to CA together and have him live with her. But with the abuse and her fearing for her life and her Dads (he’s in his 70’s. The hey have made statements of wanting to harm them frequently), she wants him gone. Preferably a ward and for them to move back to Michigan to their mom’s house.

How do we legally go about this so it’s not just a 72 hour hold? We’re scared they’ll hurt her if he’s released from that hold. We bought a camera to gather evidence of any sort and are drafting up eviction letter.

The house belongs to my friend’s grandma, but she is primarily the grandmas caretaker. But they all can agree that they don’t want him there.

Need help on how to go about this so they won’t come back to hurt anyone.