You have options depending upon the situation. You can either:

A. Brace her for the break and slowly take your distance from her. Make her see that you need to leave for the best of the both of you, that using a relationship as a crutch is not a good thing. B. Get her the help she needs, assuming she wants it, either through family, local community, organisation or local government body, and then letting them take the reins. C. Gtfo out, now.

The last one is reserved for when she tries to manipulate, control and otherwise subvert you by using suicide as a threat. This is a cyclical behavioural pattern whereby she gets validation when successfully subverting you, effectively creating a chain of incentives to continually subvert you. This means it might be impossible for you to reason with her at all and she needs someone else to do that. At this point, you really don't have a choice in the matter.

Replace pronouns with whatever you want, because this is a human problem and relationships with a basis in perlonged abuse can rarely be salvaged - at least in my opinion. If there's any dealings either part needs to have with each other, say because of shared custody, it should be with lawyers or with other representatives that can mediate.

Again, you are loved, you deserve respect, you deserve dignity, and the same with her, but if she is abusive and it's widdling down your psyche, you are actively enabling her abuse and harming yourself in the process.

I feel the need to qualify that I am not a psychiatrist, psychologist, professional consultant or social worker. I just have a bit of experience myself. You should probably get in touch with someone to try and figure out the best solution for your situation.

I wish you all the best.

Call emergency services maybe. If she's in such a bad state that it takes your mental health being damaged to keep her safe, that's a very bad position where external intervention is warranted. Or she's using that as emotional blackmail and calling emergency services will catch her bluff. Either way, it's a good option.