。
She's extremely fussy about food.
Literal
She [topic-は] food [about-には] extremely fussy.
やかましい is a synonym of うるさい in its 'fussy, particular' sense, but feels slightly stronger or more colloquial. The には (に + contrastive は) narrows the scope: specifically about food, she's very particular. 非常に (ひじょうに, 'extremely') is a formal intensifier.