Maybe talk to her and make sure she's aware of the resources she has? She may not know that pcc is an option, and that way she could make the call herself if she truly wants. Also, she may want to take advantage of Lyra if she isn't already. It won't help with the sm/gossip issue, but may help her immensely.

Considering the partner has clear mental health issues as you have stated there is no clear way to prove that your manager is being abusive. It could just be the case where the partner is mentally distressed and overreacting as a result (parent loss is probably not helping their mental state). Being a “snitch” or asking to report misconduct is not against the rules. If you are not a shift its not your job to intervene in this case and you should ask a shift to speak with the manager if they also agree and are concerned about the partners well being. No one is stopping you from calling pcc if you think the partner is in immediate danger, however it may not be what that other partner wants. Plus avoiding your boss to get to their bosses without attempting to connect first is typically a really bad idea. Overall would reach out to your shifts or manager and go from there. You have no idea if your manager has issues going on or if you are misinterpreting the situation because from my experience no one ever really knows what is happening because gossip is so twisted