Isn't Kumano saying that she would eat chocolate potato chips if there weren't any normal potato chips left?
「○○○を食べれば良いじゃない」is the typical translation of « Qu'ils mangent de la ○○○ », or "Let them eat ○○○." I think the quote also matches Suzuya's reaction about Kumano's "Ojou-samaness."
KumanooOh myIt seems like they ran out of potato chips.Well, if there aren't any potato chips,Kumano...when you received your Kai-ni, did your "Ojou-samaness" also go up...?
Ojou-sama is basically a term used to refer to young rich women, usually with the implication that these women have no common sensethen, let them eat ROYCE's Potatochip Chocolate.