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She stood on the deck with her long hair streaming in the wind.
Literal
She [topic-は] long hair [object-を] wind [to-に] fluttering-caused [and-て] deck [on-に] was-standing.
髪を風になびかせて is a vivid descriptive clause: なびかせる is the causative of なびく ('to flutter/stream'), but like 足を滑らせる, the causative here doesn't mean intentional action — the wind is causing the hair to stream. This involuntary-causative pattern efficiently puts the subject in the frame with a dynamic visual detail. The image is cinematic.