He does sit, and that's all that really matters to her. He can be as angry or frightened or fidgety as he wants, as long as there is enough of him present to listen.

Yennefer sets the bottle she'd found in his palm, the tell-tale sign for him to hold it, as she starts looking him over more closely. She places her hands on each side of his face, tilting him up to look at her as she checks his eyes, presses the pads of her fingers to the skin of his face.

He keeps talking, going on about the taint, about his power, and Yennefer is only really half-listening as she continues through what appears to be a kind of mental checklist. When she finishes up with it, her attention comes back to Mat's eyes, where she seems to check once more before letting go of him - despite the way she feels a kind of draw to keep contact, how something in her chest pulls for his attention on her and only her.

"What you're seeing is not the taint- it is not you going mad. If it were, I wouldn't be feeling it. I will ease the effects, what you're feeling and seeing, until whatever is happening eases." She points to the potion bottle in his hand. "Drink that."