She has been getting steadily better since being hospitalized.
Literal
She [topic-は] is-hospitalized [after-てから] [steadily-どんどん] [is-getting-better-良くなってきている].
Three time/aspect layers in the predicate: 良くなる ('get better'), then ~てくる (gradual development toward the present), then ~ている (ongoing state) → 良くなってきている. ~てから ('after, since') sets the starting point. どんどん is a state mimetic for steady, rapid progression.