。
She passed away yesterday afternoon.
Literal
She [topic-は] yesterday [genitive-の] afternoon [at-に] passed-away.
亡くなる is the polite, indirect verb for dying — the everyday euphemism Japanese reaches for in obituaries and announcements, where the bare 死ぬ ('die') would feel blunt or callous. Built from 亡い ('be no more, lost') + なる ('become'), it literally describes the person 'becoming gone.' Japanese has a particularly rich vocabulary for death across registers: 逝去 (formal), 永眠 ('eternal sleep,' literary), 旅立つ ('set out on a journey,' poetic), all chosen by setting and relationship to the deceased.