She does nothing but look for her husband's faults.
Literal
She [topic-は] husband's faults [nothing but-ばかり] is-searching-for.
欠点ばかり探す — ~ばかり again with its mildly negative connotation: 'always just looking for faults.' 欠点 ('faults/shortcomings') is a common Sino-Japanese compound.