Long story short; girlfriend and I were fooling around, and she started rubbing my penis on her vagina, and for about 15-20 seconds the head was inside, and decided not to have sex tonight. She's extremely freaked out, it was only the head inside, but as it's said- no one can tell when they pre-cum.
Should she be excessively worried? Is this a reason to go get the morning after pill and make sure there's no chance?
I kinda don't care for the immature responses, so please valid answers if you could.