、。
She speaks French, not to mention English.
Literal
She [topic-は] English [topic-は] of-course, French [also-も] can-speak.
~はもちろん is the everyday cousin of ~は言うまでもなく — both mean 'X goes without saying / not to mention X,' but もちろん feels conversational and unmarked, while 言うまでもなく leans bookish. The pattern works the same way: topic the obvious item with は, frame it as a given, then add the noteworthy fact. もちろん itself is borrowed from Sino-Japanese 勿論 ('certainly, of course'), almost always written in kana in modern usage. 話せる is the simple potential of 話す ('speak' → 'be able to speak'), the most idiomatic way to express 'can speak X' in casual contexts.