yeesh i know people are ragging on the guy but tbh the FL made the major mistake of saying "i love you" after the equivalent of 3 random hookups. you just don't...do that. it's actually quite normal for two adults to just hookup without intention of dating, so i wouldn't rag on the guy that much. not that the way he handled it is very...great, but the only thing the guy gave her was sex and one meal, that's it. they never had a proper date, never communicated any actual interest, just hooked up for basically random sex. he was aggressive about it but she complied and went along with it (first two are kind of dubious especially the second one, but this third time she clearly consented with that nod).
and this would be no different if the roles were reversed with the guy being the one to say i love you and the more dominant woman saying "nah i'm not interested." rather than a gender thing it's just clear lack of communication and expression of intent. one's off daydreaming, the other is attracted to the sex but maybe not for an actual relationship. so i'm not really surprised by this development (one that isn't that uncommon in romance fiction with these kinds of tropes, too).
now the story is set up for the "not interested" party to suddenly become interested in the other, although with the FL being so weak about it it'll be full of tears and boo hoo, probably damsel in distress situations and close comfort until "at last i see the light~". This kind of thing is more interesting when the other person is actually more aggressive in like "you may not be interested now, but i'll change your mind!" (assuming THAT isn't also done in a cringey way...50/50 chance on that, too hah.)
anyway, protip: don't say the big three words unless you're actually dating and COMMUNICATE.