。
She's a born musician.
Literal
She [topic-は] born [possessive-の] musician is.
生まれながらの means 'born, innate, natural' — used attributively before a noun. 音楽家 (おんがくか) means 'musician.' This is a strong compliment: her musical ability isn't learned but innate, as if she came into the world already a musician.