(First off, just to get it out of the way: she's a virgin. Of PiV sex. Many people in this thread who've had PiV sex are probably virgins of other kinds of sex, like anal sex, or something else. Chillax, people.)
So it totally doesn't surprise me that Scarlet grew up reading sexy fanfiction. As she knows, a lot of it is written by people who haven't had actual sex, so it's full of all these tropes about sexuality that aren't true but get reenforced when one virgin writes something, another virgin repeats it in her story, and so on an so forth. And the idea that sex automatically floods the female body with love hormones is one of those tropes, because in the context of the story it can seem super romantic and shit. But really, it does NOT work that way- and even if it did, as other people pointed out, there's no reason it would be limited to only that one specific type of sex.
I sympathise because I actually used to believe this. Then I had sex, and as it was happening I was like "WOW I'M HAVING SEX OMG," and afterwards I didn't become more bonded to my boyfriend at all. I liked him before, I liked him afterwards, but nothing really changed.
Scarlet, you could never have PiV sex for the rest of your life, and that would be fine! But don't get your sex info from fanfiction, please! It is not very realistic! (And the real thing is better...)