Hi Rise-up,
I understand how difficult it is to cope with the Jeckyll and Hyde behavior.
I can understand how you could shut down. Do you think that shutting down exacerbated your SO's behavior?
I found that validation/communication tools has helped me in situations similar to yours. From experience, when I ignored my pwBPD's complaints while doing housework, he became more irritated. He particularly loathes cleaning the bathroom and complained about it profusely. Using communication tools, I have said, "I understand that you do not like cleaning the bathroom, but working together makes the house work easier and quicker. If we finish it together then we will have more time to spend together. Is there something that you would rather do than clean the bathroom?"
Perhaps you could do something similar with your SO? Maybe compromise about the cat litter and trade off that chore, since she hates doing it? Have you tried using communication tools with your SO? Here is an article on validation that is very helpful.
Communication using validation. What it is; how to do it