A very interesting parallel Suselle and Krusie share is that, while Kris and Noelle are clearly jealous of the other's relationship with Susie, they handle it in a very interesting way: instead of letting it inspire them to sabotage the other's relationship, their envy drives them to keep building on their own!
If you actually pay close attention to the scenes above, you'll see that Noelle and Kris don't say those things because they don't want the other to stop having a close and loving relationship with Susie; THEY WANT THEIR OWN RELATIONSHIP TO BE EQUAL TO THE OTHER'S!
Noelle isn't telling Susie they shouldn't go to the diner with Kris; she's saying she would like to have her own trips to the diner with just her and Susie, like she and Kris do now. And in the scene on the right, Kris isn't telling Susie she should carry them INSTEAD of Noelle, but that she should carry them AFTER Noelle so that they can listen to her heartbeat.
That's because when Kris and Noelle see Susie talking about her special moments with the other and how much it means to her, they think to themselves that it's because the other's relationship is deeper and more intimate than their own, and that's why they encourage Susie to do the same thing that she got to do with the other!
