。
She has a beautiful set of teeth.
Literal
She [topic-は] pretty teeth-alignment is.
歯並び ('arrangement of teeth, dentition') decomposes as 歯 ('tooth') + 並び ('lining-up,' from 並ぶ 'to line up'). The compound describes the visible alignment and spacing of teeth — a culturally interesting topic, since traditional Japanese aesthetic standards historically had less concern for perfectly straight teeth than Western (especially American) standards do; 八重歯 ('snaggletooth, double tooth') was even considered cute in pop-culture beauty ideals through the 20th century. Modern orthodontics have shifted preferences, but the cultural specificity of dental aesthetics is worth noting. The bare noun-predicate structure 歯並びだ avoids needing a separate verb of possession — Japanese can directly state 'is X-feature' for descriptive observations.