Every labia and clitoris gets larger the more horny the woman gets. Those butterfly labias get larger until she cums. If her clit is sticking out of its hood after you tongue her or fuck her for long enough to cum, she may not have faked it. But the other clues, like blushing of her face and seeing her back arch and knees open, then close around your head are good signs your tongue did a good job.
