。
She's been working non-stop.
Literal
She [topic-は] work-non-stop is.
~づめ (also written ~詰め) is a suffix attached to verb stems expressing continuous, unbroken action — 'nothing but X.' 働きづめ means 'working without a break.' Other examples include 立ちづめ ('standing the whole time') and 座りづめ ('sitting non-stop'). It's a vivid, colloquial way to emphasize the relentlessness of an activity, distinct from the more neutral ~続ける.