。
She didn't show up before the concert ended.
Literal
She [topic-は] concert [subject-が] ends [until topic-までには] didn't-come.
~までに sets a deadline ('by the time'); the added は in までには contrasts this deadline against other possibilities — the implication being 'whatever she did afterward, she certainly hadn't arrived by then.' やってくる is a compound of 来る ('come') and やる that adds a sense of arrival or appearance, closer to 'show up' than the neutral 来る. The negative やってこなかった captures the absence as a noticeable event.