。
She hopped right over the little stream.
Literal
She [topic-は] stream [object-を] lightly straddled-over.
ひょいと is a state mimetic (擬態語) for a quick, light, effortless movement — a nimble hop or casual flick. またぐ (跨ぐ, 'to straddle, to step over') with を marks the obstacle being crossed. 小川 (おがわ, 'stream, brook') uses the diminutive prefix 小, indicating a small waterway. The combination paints a picture of casual agility.