Can My Partner Put A Restraining Order On His Mother Who Kidnapped His Dog?

Location: California, US
Hey all. I (22F) and my partner (23M) are both enraged and stuck. By the title, yes, my partner's mother kidnapped his dog. Forgive me, this is my first time posting like this and I am rather angry right now so if things are confusing, that's on me.

Some history- My partners mom is an authoritarian parent. She, according to him, was actively physically abusive as a child, and now that he's moved out of her house, she seems to have stopped behaving that way with his siblings. She has cameras in her home, tracks her kids, and has a history very strict and aggressive with her family.

Last year, we traveled to visit her and the rest of his family. We chose to bring out 5-month-old puppy, who is a notoriously small dog and to this day is barely larger than a chicken. While there, the dog was strangled by her youngest, a two year old. We took her to the hospital where she was having seizures, difficulty breathing, and various other pains. She had a concussion, and I ended up taking care of her the following day where she had more seizures and completely stopped breathing, requiring CPR. To this day she has some neurological difficulties walking and retaining information that she learns, but she's a happy dog, and we don't blame her kid because we know that children have poor motor control and poorer listening skills.

We were told by friends to sue her for medical costs, 2500$ was spent for a single night and she refused to take accountability for her child's actions, blaming us for not scolding her. We let things lie under the rule that the dog will never go up there again.

Last night, while he was visiting some family away from home, she sent him a message saying that she kidnapped his dog, then a picture of the child holding the dog. Apparently, she had visited where he was staying with family, and while there she simply took the dog. Her "conditions" were that he must visit her.

Thus, that leads to my question. As anyone could expect, we're angry at her. She's not an idiot, she knows what happened and she for sure sent that photo to aggravate us. She has behaved like this before, and I'm done. I'd want to sue her, but I'm not sure of the charges necessary and if we'd even be able to afford a lawyer. Instead, I want to consider putting a restraining order on her. There's other issues involving her having control of some funds of his and further identification, but that we can figure out further with our lawyer if we choose to proceed. Any words could be helpful at this time.