。
She didn't go out and stayed home all day.
Literal
She [topic-は] not-going-out all-day home [at-に] was.
出かけないで (without going out) uses ~ないで to express 'without doing X' — she stayed home by not going out. 一日中 (all day long) is a useful time expression: 一日 (one day) + 中 (throughout). The simple いた (was) at the end describes a static state — she existed at home for the whole day, doing nothing noteworthy enough to mention.