She kisses you fiercely as you pump your cock into her for all you are worth.
And she gets extremely excited also, saying: "Yes, James! Fuck me! Oh yes! Harder! Harder! Oh yes! Yes!"
She moves her legs down so that her panties press against the back of your neck, and then she draws her feet together, so that you start to feel like her panties are going to choke you to death as you fuck her. You worry that she is trying to kill you this way...