The humiliating position of presenting her bare bottom to the cane with her panties down and showing her cunt is an important part of discipline.
She'll be glad to finally be fucked from behind so the painful caning strokes stop.
When using a stinging cane, and this is generally recommended due to its unparalleled educational effect, a punishment will only be effective if it leaves clearly visible marks, that is, the typical double, strongly reddened bumps. Otherwise it is a deception.