After the two of you shrunk, and your new "captor" announced with a radiant smile on her face which could have easily been hiding some malicious intent, that "one of you" would have the pleasure to experience sex one last time, you immediately knew that she wasn't talking about you.
It was simple deduction really, as the other guy who got shrunk along with you, clearly didn't shrink down quite as much than you, and, if she'd had the intent on feeling anything at all, it was bound to be from the taller of the two.
Your intuition was validated the moment she started stripping down, spread her toes and shoved you between the weave of her fishnet stockings, captive now between her toes.
The world began to shake around violently as soon as she started moving, the motion sickness of it all had you grasping for dear life, just hoping she wouldn't squish you before she got on her bed.
You did see her however pick up your new acquaintance, and as she sat down on the bed, spreading her legs wide open, put him down right in front of her vagina.
"That should do just fine" "you don't seem to have any trouble reaching it" she said as she laid back ...
"Now get to work"
As the two of them were having at it, her feet began moving with more and more violence as she was reaching orgasm, as you were left there between her toes, riding the motion, trying your best to not throw up ... and worse, not slip back between the sole of her heels and the sole of her foot. In the heat of the moment, clearly forgetting you were even there, watching it all happen from afar.