。
She's good at drawing.
Literal
She [topic-は] picture [subject-が] skillful-is.
うまい applied to a person's performance means 'skillful' — slightly more casual and warm than 上手, with a faint oral or 'street' flavor (it doubles as a colloquial word for 'tasty,' from the same root). The pattern X が うまい = 'good at X' looks unusual to English eyes because 'X' is marked as a subject, not an object: that's because うまい (and 上手, 下手, 得意, 苦手) are state predicates — they describe the speaker's relation to the activity, with the activity as a kind of subject of the assessment. So 絵がうまい literally pictures-itself as 'pictures (subject) skillful (predicate).'