。
She'll probably get better soon.
Literal
She [topic-は] soon better-become [probably-だろう].
じき (直) is an adverb meaning 'soon, in a moment, before long' — conveying near-future imminence without specifying an exact time. よくなる is the standard pattern for 'getting better': adjective stem (よく from よい/いい) + なる ('become'). Productive across many adjectives — 大きくなる (grow bigger), 悪くなる (worsen). だろう adds the speaker's subjective probability — 'probably, I'd bet' — keeping the prediction tentative rather than asserted as fact. A natural register for reassuring someone about a recovery.