。
She's working hard.
Literal
She [topic-は] with-all-one's-might is-working.
A compact, vivid sentence: 一生懸命働いている — 'wholeheartedly is working.' ~ている here is on an activity verb (働く, 'to work') and reads as the progressive: she is right now in the act of working hard. The same form can also be habitual ('she works hard regularly') depending on context. 一生懸命 paired with 働く is one of the most common adverb-verb combinations in everyday Japanese — a near-default way to praise dedicated work.