。
She never misses a bargain.
Literal
She [topic-は] bargains [as for-には] missed-eyes [subject-が] don't-exist.
抜け目がない is a fixed idiom literally 'no gap-eye exists,' meaning 'shrewd, sharp, with nothing escaping notice.' 抜け目 ('an oversight, a missed spot') is a noun built from 抜ける ('slip out, escape') + 目 ('eye, point'); it's almost never seen outside this idiom. The doubled は in にはand the topic 彼女は creates a contrastive scoping ('when it comes to bargains, at least'). For shopping in particular, this idiom often carries a positive note of admiration — being savvy with money is a respectable trait — though context can flip it to a faintly pejorative 'cunning.'