Firstly, i am so sorry both of you go through this. Secondly, I am glad to hear you’ve found your soulmate.

Is she medicated? I noticed a big change in my mood swings (I do not have cyclothymia, at least not that I am aware of, or bipolar) when I was put on a high dose of mood stabilizers and a low dose of anti psychotics. If she isn’t, this could drastically improve her quality of life. If she is, perhaps it’s time for a change in her dosage.

I am no expert on this, I just know I have experience with very awful mood swings from mental health problems... But perhaps a way that you could approach this differently is to explain in the moment that she is experiencing a mood swing and is acting differently and treating you unfairly/making you uncomfortable? Ask her how she’s feeling and what’s going on, rather than just going with the mood swing? I feel like this could have negative consequences and she could break down or go into a fit of rage, so it’s up to you whether or not you want to try.