。
Can she ride a bicycle?
Literal
She [topic-は] bicycle [on-に] able-to-ride [question-か]?
乗る ('to ride, to board') takes に — you 'ride into' a vehicle in Japanese, parallel to a static spatial に for 'on/in.' The potential 乗れる ('be able to ride') is the regular potential of a Group I (godan) verb (乗る → 乗れる). Made polite with ~ます, then questioned with か — a textbook polite question.