。
She is believed to be from China.
Literal
She [topic-は] China [possessive-の] origin is [quotative-と] is-believed.
~と信じられている uses the impersonal passive to express a widely held belief. 中国の出身 ('from China / of Chinese origin') uses 出身 ('origin/hometown') — a standard word for expressing where someone is from. The construction neatly packages hearsay into a formal statement.