。
She recoiled when she saw the snake.
Literal
She [topic-は] snake [object-を] seeing retreated.
蛇を見て退いた — she saw the snake and withdrew/recoiled. 退く (しりぞく or どく) means to retreat, step back, or withdraw. The て-form 見て chains the seeing with the retreating as cause and effect: the sight triggered the recoil. The reaction is instinctive and physical — a vivid verb for that involuntary backward step.