I would say, Kyuui's perfectly able to notice the spiked drinks and say a warning to the group and/or refuse to take her own drink, as the suggestion doesn't prevent that.  So no, it wouldn't be negated; she'd still have to follow along with what Zamala says for the duration (though if any of Zamala's commands would put her in danger though, then yes, she'd be allowed to break it), but is otherwise perfectly able to do whatever she wants.