She uses a piece of her clothing

Still kneeling, she spins around and reaches out to grab a piece of her discarded clothing. Unwittingly giving you a full view of her pert, tight, teen arse. You want nothing more than to reach out and spank her peach, but she turns back around and places the undergarment over the pool of cum on the floor, dabbing at it.

All in good time. You think to yourself.

Within a few moments, she has cleaned up the 'spillage'.

"Good girl." You lean down and place a tender kiss on her forehead. "You're the best sister a person could hope for."