。
She didn't visit anyone yesterday.
Literal
She [topic-は] yesterday anyone [also-も] did-not-visit.
誰も + a negative verb forms the universal-negation pattern 'no one / nobody' — 'anyone' in English plus a negative collapses into 'no one' in Japanese with no separate word for 'no.' The same template gives 何も~ない ('nothing'), どこも~ない ('nowhere'), and いつも~ない ('never'). 訪問する is the Sino-Japanese verb for visiting in a more formal register than 訪ねる; common in news, business, and written contexts.