Manga makes it pretty simple and obvious, which becomes more clear once you realize kishi is over obsessed and simplicity with parallels that plagues this manga. Anyway, Sakura had lust over sasuke's edgy personality much like naruto had grudge for the same reason. her lust turned into love(bonded would be a better choice of words) once she got to see sasuke when he was vulnerable during the encounter with orochimaru, then reinforced her love (or rather gave her love a reason) when she realize sasuke's cs1 corrupted him which drove her to want to save him from his darkness. kinda like how naruto despite previously wanting to bring sasuke back to the village, it wasn't until sasuke opened up and call him "his friend" that gave naruto his own true bond/motive. The creepy part honestly, is that sakura said she wanted to join sasuke as a rogue, kinda wish kishi kept with that idea, cause it reminds when hinata said she didn't care if she was selfish, all she wanted to do was be with naruto. it shows that love is irrational, it doesn't care about right or wrong.