。
She has pretty eyes.
Literal
She [topic-は] pretty eyes [object-を] have-as-feature.
~をしている in its descriptive sense — used to attribute a physical feature to someone, where English would just use 'has.' Common with body-feature descriptions: 大きな目をしている ('has big eyes'), 青い目をしている ('has blue eyes'), 長い髪をしている ('has long hair'). The を marks the descriptive feature itself, and している (literally 'is doing') functions almost like a copula — Japanese uses this construction to lock the feature in as something the person inherently exhibits, not just possesses.