Don't mind me, just going to vent for a second.
She could have just used search on the tea. It apparently lets her analyze the ingredients of things anyways, so wouldn't that be the first thing to come to mind when you think "I wonder if they put something in my tea"? If something comes up as too complex to analyze just freakin' ask what they used in it. If they get suspicious you can easily just say "I saw mine was different so I was curious as to what the difference was".
It's not like you can say she didn't have the chance to, since nothing was stopping her from doing it after getting yelled at. Besides, if it turns out there is something too complex to use search on, you've got plenty of justification to be suspicious. Who the hell would put something in tea that's so complex it couldn't be immediately analyzed by her high-level search ability?
Also, why weren't the other three paying any attention? She was standing right next to Kaido when she looked at Mamari. What, did he say "Is that so?" and immediately turn around and wander off out of earshot to let her be the only person that saw Mamari's smug bitch grin for the sake of the plot?
And boy, he sure was angry at her for being concerned wasn't he? The hell's this "Do you wish to pin my disciple as the villain?" shit? It's not like she said a single goddamn thing about it. He didn't even let her speak! It's natural to go "Huh, that's weird" when a person tells you they're using an ingredient that's needed for poison but refuses to tell you about it. Thinking something's strange when they prepare tea that's different from everyone else's immediately after is hardly inappropriate! Wouldn't the correct response be "you don't have to be worried about that"? If it turns out he doesn't have anything to do with Pit Viper and wasn't trying to cover for her I'm going to be Livid.
God.