。
She left the stage last year.
Literal
She [topic-は] last-year stage [from-を] departed.
舞台を去る ('leave the stage') is conventionally read as retirement from the performing world — actresses, dancers, stage performers 'leave the stage' the way English-speaking pop stars 'hang up the mic.' The を here marks 舞台 as the place departed (a separative use, not the direct object of an action) — the same を appears in 家を出る ('leave home') and 大学を卒業する ('graduate from university'). Reading it as a literal walk-off works grammatically but loses the more interesting career-ending sense.