This went pretty well and has been pretty good so far. She hasn't tried to test it yet but I'm feeling much better about enforcing this one.

I've been more assertive about other boundaries as well and am trying to do a lot of work to form and write down value-based boundaries instead of just reactive behavior ones.
e.g. — I value love and kindness. I will not accept being treated unkindly and without respect. If this happens I will not participate, try to de-escalate, and remove myself from the situation.
e.g. — I value individuality and responsibility. I will not accept being devalued as a person or having my words twisted. If this happens I will stand my ground, reinforce that I said what I said and what I meant by it, and will not get drawn into an argument about it. If emotions get high I will remove myself from the situation.
And things like that. It's tough but validating, and I finally feel like I have a way out of this fog, or at least a way to take myself back.
Time to go chat with my therapist about this, wish me luck.