It's funny how I can't see into FMC's personality. I can't tell what her motives are anymore lol
But it's very simple and obvious? She wants the D.. Deep Childhood Friendship with him, eventually followed by
marriage lifelong childhood friendship vows and also those very close childhood friends bonding activities that all childhood friends in CF romances or some wholesome hentai end up doing.
IMHO, at first she started with wanting to have friendship part of that ideal youth she read about in her manga, just like other kids want steamy romance out of their favorite shoujo manga (or even ecchi romcom) or starting wacky school club out of manga with new friends who have same nerdy interests and adventures like fighting the school to not disband the club, or other "seishun" stuff that often get semi-mythical status in manga. Then she started to fall for him, and is now both rationalizing it as "being really close" to avoid having to face her new feelings, and at the same time using it as an excuse to get closer to him (like right now in bed
) without having to ask him out or date him. After all, she was supposed to a bit of shy bookworm that has trouble connecting to others in real life, despite how bold she always is with male MC.
She may also be afraid that romance will endanger her friendship with him, which is a valid fear. Changing from friends to lovers comes with its own issues.
I mean, look how long Nagatoro's couple were pretending they're not going out, and those were supposed to be teenagers close to adulthood. That whole "couple but not calling it dating" is pretty normal in manga, too normal if you ask me.