Huh. I had to look back at post #2802754, and indeed it's not only possible, but implied that Big Sis was doing some "self"-groping.

When it's with your lover, Freaky Fridays are best spent discovering what your significant other will enjoy best when it comes to the body's pleasures.

It's fitting to the character of the older sister to diligently do her homework for the sake of her sister's future in this kind of circumstance. (lol)