Anyway it's my personal headcanon that Kim had a crush on Ron since at least early season three but gave up on it after Emotion Sickness because the events of that episode made her think he didn't like her back (rather than the truth, that he was scared of how a romantic relationship might ruin their friendship). In So The Drama rather than referring to Ron as her friend, she refers to him as her just-a-friend, which is significant because it suggests she'd been hoping to go to prom with him as a date. And then when Eric showed up, what made her choose him over Ron wasn't his looks or his motorcycle or his athleticism, but that he was open about liking her as more than a friend (and also probably because Bonnie wouldn't be a dick about Kim wanting to go to prom with Eric). Meanwhile Ron had at least some romantic feelings for Kim since Emotion Sickness (and probably before that, but never stopped to consider them until then) but only realised how serious they were when she started being openly smitten with Eric.
