Hello Unfair-cow, welcome to the group

It's good that you both are in couples counseling. How soon into the relationship did you see a need for it? Were there any red flags? And how many sessions have you gone to so far?
Sorry for so many questions right off the bat. Just getting more of a sense of where you both are at.
I will comment that sometimes the CC (couples counselor) may seem like s/he isn't "enforcing" anything on the pwBPD or isn't "calling them out" on their
ridiculous behavior. Depending on how far into sessions you are, that may actually be a therapeutic technique to get buy-in from the more difficult partner. So, there is a possiblity that the CC knows that you're the saner one, and is trying to get your partner to stick with it by showing empathy or seemingly "giving her a pass".
Not sure if that is your exact scenario, I'm sure when you reply you can fill me in on if that seems to fit or not.
Regardless, not every CC has experience with PDs so it's very possible that your CC is in over his/her head.
I am sick of being perfect one day and then the most toxic and abusive person to ever exist the next.
That is a really common experience for those with partners with PDs -- the rapid shifting between you being "painted white" and on a pedestal, and "painted black" and literal demon spawn. pwPDs typically have a poor to non-existent sense of self and have harmfully intense, vacillating emotions that seem to define them, their relationships, and their memories/experiences. Without long term focused work in a modality like DBT, it is likely your partner will continue those perceptions and behaviors.
That being said, there are tools and skills you can learn and practice that can mitigate the effects of your partner's behaviors on your life. Have you checked out our section on "When a partner has BPD"? Lots of articles to peruse:
https://bpdfamily.com/portfolio-4-colsgive it a look and let us know how you've been doing lately.
Again, welcome;
-kells76