find quarrel in a straw 鸡蛋里面找骨头；吹毛求疵；找碴儿

【例句】
She is not one to find quarrel in a straw.
她不是吹毛求疵的人。

Don't find quarrel in a straw, it's already quite difficult for him.
不要鸡蛋里挑骨头，他已经很不容易了。