。
She didn't show up.
Literal
She [topic-は] did-not-appear.
現れる is the intransitive 'to appear, show up, materialize' — used both for physically arriving (彼が現れた, 'he showed up') and figuratively for things coming into view (虹が現れた, 'a rainbow appeared'). In the negative past 現れなかった, it takes on the specific 'failed to show up at an expected place or time' reading. The sentence is striking for its brevity: subject + negative verb, full stop. Japanese can leave the time, place, and expectation entirely implicit — the listener fills them in from context.