。
She's never been abroad.
Literal
She [topic-は] overseas [to-に] go past-experience does-not-exist.
The pattern V-た+ことがない is the negative of the experience pattern V-た+ことがある: 'have never V-ed.' Literally 'the fact of having V-ed does not exist.' This is the standard way Japanese reports the absence of a particular life experience — 食べたことがない, 見たことがない, 行ったことがない. Note it specifically denies experience, not capability or willingness; for those you'd reach for ~られない or ~たくない instead.