damn what’s wrong with you people rooting for a rival the minute they pop up in this comfy slow-burn romance
Because she sucks ass and didn't earn or deserve any of the affection she is receiving. This is the same girl who completely ignored the dudes confession and ignored him for weeks and only now come to "like" him becuase there is competition. Authors use rivals to stir up some progress but in this case, it made the story a huge disservice.
Reason is, as soon as a more well rounded character with actual emotinal intelligence shows up, people tend to completely divert their attention to her instead.