。
I wonder what ever became of her.
Literal
She [topic-は] how became [I wonder-のだろうか].
どうなった ('what became of (her)') asks about an outcome already decided but unknown to the speaker — past-tense reflection on an unresolved fate. The ending のだろうか stacks explanatory の, conjectural だろう, and question か — a classic 'I wonder if...' frame in slightly elevated speech. The か is what tilts it toward an open question rather than a settled musing. Often used about someone the speaker has lost touch with.