The boy threw a comb behind them, which became mountains with thousands of teeth, which the nixie got through with great effort. The girl threw a mirror behind them, which became a mountain too slick for the nixie to climb. She went back to get an axe, but before she could chop through the mountain, they escaped.
The boy's comb became mountains with sharp edges, which the nixie overcame with difficulty. The girl's mirror turned into a slippery peak that the nixie couldn't scale. She retrieved an axe, but before she could chop down the mountain, they broke free.