。
She'll surely recover.
Literal
She [topic-は] surely will-recover [probably-だろう].
回復する ('recover, regain health') is a Sino-Japanese verbal noun — 回 ('return') + 復 ('again, restore') — covering recovery from illness, injury, or any setback. It's broader than 治る ('be cured'), which is more medical, and overlaps with 元気になる ('get well') in casual contexts. The combination きっと~だろう projects high confidence about the recovery, with the kind of optimism that's common when offering reassurance to a worried party.