。
She has plenty of youthfulness left.
Literal
She [topic-は] youth [object-を] sufficiently is-having.
若さを持っている (to have youthfulness) is slightly more static than 若さを保っている (to preserve youthfulness) — 持つ describes possessing a quality, while 保つ emphasizes actively maintaining it against the passage of time. Both are acceptable ways to describe someone who still looks young, but the nuance differs in agency.