。
She's the perfect fit for the role of Juliet.
Literal
She [topic-は] Juliet [genitive-の] role [object-を] perform [for-purpose-of-のに] suitable [is-だ].
A Shakespeare reference: ジュリエット points to Juliet of 'Romeo and Juliet,' the canonical romantic ingénue role in Western theater. Japanese theater has a long history with Shakespeare, dating back to Meiji-era (late 19th century) translations and adaptations; Romeo and Juliet in particular was an early and frequent staging target. 役を演じる is the standard collocation 'to play a role,' literally 'to perform a role.' The construction Vのに適任 — '[verb] + のに + 適任 (suitable)' — uses のに in its purposive function ('for the purpose of'), which is distinct from the more common concessive のに ('despite, even though'). Same surface form, completely different meaning, distinguished by what comes after: purposive のに pairs with adjective predicates (適任だ, 便利だ, 必要だ); concessive のに pairs with full clauses.