。
She can speak English very well.
Literal
She [topic-は] very skillfully English [object-を] speak-can.
話せる is the potential form of 話す ('to speak') — concise alternative to the wordier 話すことができる. Note that English ('英語') stays with を because it's the object of 'speak' even after the verb shifts to potential; some learners over-correct to が, but と話す-style verbs keep their original を-frame in the potential.