。
She feigned innocence.
Literal
She [topic-は] innocence [object-を] pretended.
無邪気を装った — 装う (よそおう, 'to pretend, feign, disguise') is a literary verb. 無邪気 (むじゃき, 'innocence, naivety') is a na-adjective used here as a noun.
。
She feigned innocence.
She feigned innocence.