。
She kept up her work at the bank.
Literal
She [topic-は] bank [at-genitive-での] work [object-を] continued.
での is the genitive-attributive form of で — the locative particle で plus the noun-modifying の — yielding '[the] X at Y' (or 'Y's X' where Y is a place where the action happens). 銀行での仕事 means 'the work that takes place at the bank.' This composite particle stack is essential for turning a で-marked locative phrase into a noun modifier. Note that 勤める ('be employed at') would take its workplace with に as institutional affiliation (銀行に勤める, 'be a bank employee'); the での pattern here instead frames the bank as where the work physically happens — action location rather than institutional anchor.