@ghostt well, yeah. but it was 10 years ago and in ch120 you can see her blushing already. so its quite possible that he was her first love in some sense. she even spent 10 years of her life trying to match him. and there is nothing wrong with a pair with ~10 years difference in age if they both adults(she doens't seems like underage to me right now)
I mean there is much more plot behind it than in MCs case where 3 girls already fallen for him just because he is MC