。
She has the most stunning figure I've ever seen.
Literal
She [topic-は] until-now seen [experience-こと]-also not-existing splendid style [object-を] is-doing.
スタイルをしている is a curious calque-meets-coinage: スタイル is the loanword 'style,' but in Japanese it has narrowed almost exclusively to mean 'physique, figure, body shape.' Combined with をしている — the resulting-state form of する, meaning 'to be in a state of having' — the phrase frames the figure as a quality the person possesses. Parallel to 顔をしている ('have a face'), where the same をしている turns a body part into a possessed state. 見事な ('splendid, magnificent, masterful') is a strong evaluative adjective, originally praising skilled craftsmanship and now applied broadly.