While your scenario might be possible, it’s also equally possible the girls just didn’t like one another for whatever reasons we don’t know about. Just personality conflicts type of a thing. It’s hard to extrapolate the dynamics based off of just this teeny tiny account. I think it’s wishful thinking to decide this is what is going on though. I would say Dylan was the type of guy that was 99% nice to just about any girl that was nice back to him though. And, according to his writings, he had multiple crushes on unknown girls. CHS was very large and there were a lot of girls, and plenty that he had ‘nice’ interactions with in class on a daily basis (including Val Schnurr). So, given all of that, it’s difficult to really pinpoint exactly if the reasoning the two girls didn’t get along is because of catty jealous rivalry. We also have to consider too that Robyn had a couple of guys she interacted with as friends and while in Dylan’s company. For example, she’d walk from Calculus class with Dylan and Joe to the 3rd hour class at which point they split up and went to each of their classes. I honestly do not see Robyn as being mono-focused on Dylan nor jealous concerning his interactions with other people including other girls.