yeah, there's no chance he actually drank that tea as is, he either faked it or made something to negate the effects of her poison, and now is playing along to see just how deep the rabbit hole goes
more likely he faked it, useful as that particular poison seems, there was always a chance she'd use something else on him initially, after all she can feed him as much mind control poison as she likes if he's paralyzed or sleeping and made helpless at first (a good villainess would have done so, anyways. she *should* have predicted he'd know about the mind control poison after the incident with his father brought him to her)