
But why did the protagonist throw the cabbage that was actually a lettuce down the cliff?

Because the protagonist was tricked by the man selling the cabbage, he said if she threw a cabbage down a cliff, she'd get unlimited cabbage from his shop, so she bought a cabbage to throw down the cliff. It was late at night so the protagonist couldn't see well in the dark. And it was just at the cliff when the protagonist throws the cabbage did they realise it was actually lettuce in the moon light.
She'd been tricked and was now on a journey to get revenge, in the second book of course.
Ugh. This skipped out the music scene and the embroidery scene.
Those were two of my favourites, what a pity.