Things I noticed while playing around with Nettie.
I got poisoned and failed her persuasion check and failed the reroll. The dialog ended, and I talked to her again, at which time she let me choose the persuaion/intimidation/etc again. I failed the persuation checks again.
Then, as I gave up looking for a way out without combat, I found out that Knock Unconscious doesn't put me into combat. So I could Knock Unconscious on Nettie, she would take damage, run a lap around the room yelling for help, then come back to her chair. Then it's just rince and repeat until she finally is knocked unconscious.
Then I loaded the game and ended up in combat. But she started the combat with some knock back spell, and half my party (of four) were knocked outside of the room. So I was not only stuck fighting her with half my party, after the combat my party was still on the two sides of the door.

I'm not sure if either or both of these are working as intended.