。
She was clad in black.
Literal
She [topic-は] black-clothing [object-を] was-clad-in.
まとう ('to wear, to be clad in, to drape oneself with') is a literary verb favored over the everyday 着る — it's used in storytelling, news, or stylized description. 黒衣 (こくい) is the formal Sino-Japanese reading of 'black clothing,' often associated with mourning, secrecy, or stage hands in kabuki (where the same kanji read くろご refers to the black-clad assistants who move props in plain sight, conventionally invisible to the audience). The combined effect of まとう + 黒衣 conjures a scene of high drama or solemnity.