She's so picky that she even measures the thickness of each slice of bread.

picky 是形容词，由动词 pick（挑选）加上后缀 -y 构成，表示"过分讲究的、爱挑剔的"。后缀 -y 常用来构成形容词，表示"有...特性的"或"倾向于...的"。