Avoiding the topic just makes her more angry and belligerent.
Don't worry about this... .they are trying to get you back in line.
If you don't want to discuss something... .make it about you and exit. "I'm not able to discuss this right now. Is there something else you would like to talk about?"
If they keep hoping to bad topics or blaming let them know that you are not able to discuss controversial topics right now... .
Don't blame them... .
Leave the reasons vague... "controversial"... ."upsetting"... .that kind of thing.
Now, when you perceive they have calmed. Get two glasses of water (or a cup of tea, coffee)... hand them one.
You are not being overly friendly. Just ... "Hey... was thinking about you. I've got some time if there is anything you want to discuss... ."
Note: You have nothing you want to discuss right now... .this is about your partner feeling heard.
If they start ranting, blaming... .let them know they are heard and ask them about a proposed solution.
Work on how you word it... .but a great way to break this up.
1... You hear them and understand their feelings
2... You feel differently about the subject
3. You support them taking care of themselves (vice you taking action to take care of them)
If you keep sending them emotional support... .but leave action to them... .many issues evaporate.
FF