。
Despite her low pay, she works hard at the company.
Literal
She [topic-は] cheap salary [despite-にもかかわらず] that company [at-で] with-all-one's-might is-working.
~にもかかわらず ('despite, in spite of') is the formal/written counterpart of casual ~のに. Built on かかわる ('relate to, concern') in negative + も — literally 'without regard to.' The clause-final 一生懸命働いている paints the contrast clearly: diligent effort despite poor compensation — a frame Japanese workplace narratives lean on heavily, sometimes admiringly, sometimes ironically.