Some boundaries don't need to be communicated, and some are best NOT communicated, especially when the other person is drunk and irrational.
If you need to get away from her because her behavior is upsetting her, go.
That's it, just go. You don't have to explain why you are doing it. It's pretty unrealistic to expect her to change her behavior or to agree with your need to get away from it. The boundary is that you do not stay in a situation that is upsetting you.