I don't get it. Why bother making her ability disappear at all? What value does that add to the narrative? Considering it's the only really unique aspect of the story (which is printed in three colours just to support that aspect!), I don't see why the author would make overtures of removing it.
Because she doesn’t really need that kind of power,
Part of me is thinking "so what?" because characters have things they don't "need" all the time! But really...
in the first place the power was used as a catalyst for why she mistrusts love in the first place,
... she never needed it to begin with, because...
her being overtly aware of people’s feeling towards others and especially towards her put her in a bad position since she doesn’t know what do in those situations nor does she actually know if it’s even right at all.
...I really don't feel the arrows changed or enabled that any more than just being observant and talking to people like a normal human would have. Nearly this exact same story could have (and almost certainly has in the past) been written without the supernatural element. If we're being really, brutally honest with ourselves, arguably the most unique effect the arrows have had was allowing her to notice concealed shady idol stalkers...
And even if she did grow to up to use it properly, no one really needs that kind of power in their life because people shouldn’t need to rely on a crutch like that if they want to function as normal person, lest they become someone who is incapable of making decisions or pursuing relationships with people unless they find that reciprocation of their feelings are guaranteed.
The conflict you outline here sounds much interesting than dismantling the core conceit of the entire story up to this point to turn it back into an ordinary schoolgirl love triangle indistinguishable from the rest. That's the entire issue. That's why I don't understand what this change adds to the narrative.
From my perspective this is a significant downgrade in story potential.