。
She became a great painter.
Literal
She [topic-は] great painter [to-に] became.
画家 ('painter, visual artist') uses the productive ~家 suffix — same morphology as 詩人, 音楽家, 政治家. Note 詩人 itself uses ~人 ('person of'), not ~家 — a vestige of the older 'master of poetry' framing. The pattern Xになる (where X is a profession with な-adjective modification) is the textbook 'achieved this status' frame.