。
She has crooked teeth.
Literal
She [topic-は] tooth-alignment [subject-が] bad.
歯並び ('row of teeth, dentition') is a verb-stem-plus-noun compound: 歯 ('tooth') + 並び (stem of 並ぶ 'line up, be arranged in a row') = 'how the teeth are lined up.' 歯並びが悪い is the standard idiom for 'crooked teeth' or 'a bad bite.' Until relatively recently, less attention was paid to orthodontic alignment in Japan than in the US — a slightly crooked or canine-tipped tooth (八重歯) was even seen as cute or charming. Modern standards have shifted toward orthodontic correction, but 八重歯 retains its appeal.