、。
She slipped when crossing the road.
Literal
She [topic-は] road [object-を] cross [when-とき], foot [object-を] slipped.
足を滑らせる ('to let one's foot slip') uses the causative form ~させる, but not to express intentional causation — instead it describes an involuntary, uncontrolled event. This is a productive pattern in Japanese where the causative conveys accidental or regrettable outcomes rather than deliberate action. The structure 道路を横断する uses the more formal 横断する rather than the everyday 渡る, giving the sentence a slightly reportorial tone.