。
She witnessed the crime.
Literal
She [topic-は] that crime [object-を] witnessed.
目撃する ('to witness firsthand') is a sino-Japanese compound built from 目 ('eye') + 撃 ('strike, attack') — the same 撃 in 攻撃 ('attack') and 出撃 ('sortie'). The image is of the eye 'striking' the scene, capturing it. Common in news, police, and legal Japanese (目撃者 = 'eyewitness'). Compared to 見る ('see') or 見かける ('catch sight of'), 目撃する carries weight — what you witness with this verb is consequential, often something you'll be asked to testify about later.