@Jjnurui she starts paying attention to him because of the heart and i feel like her feelings just naturally develops over time because she's been looking at him so much so to answer your question, the heart is sort of the trigger but it's not the reason she likes him.
usually (well imo), feelings tend to develop when you start paying attention to someone more than usual. At first it was just something small that they do i find interesting and then I'll start paying more attention without any romantic intentions/feelings really and then one day i just realize, 'oof i have a crush on them'
i feel like logically, if she were to like him bcos of the heart, she would see him as more of a son because she has his father's heart if that makes sense lol.