Panel 1: April's stance says "Yeah, what? Make it quick, stalker-girl!" But the way her mouth is drawn says, "Aw...My pet special-needs student!"
Panel 2: April is about to fumble her binder. But why does she look so surprised? Shannon already told her that her getting an email would be a miracle. Oh, wait: that was right before Gerald barged in, so his presence caused April to forget everything else. But notice how Shannon says, "nobody in mainstream." Is that the same as nobody at all? It can't be that she's the only one of the SN kids who can send and receive emails. So does she disregard communications with them? Or maybe they don't associate with her...because they're offended at her social climbing and dismissal of them.
Panel 3: Cookie Monster: "A couple of days?! How retarded is she?"
Panel 4: Jesus H. Crimeny. A hug, just for the act of sending an email. Not because April shared anything significant. Not because they've been emailing for a while, and the developing friendship is bringing joy into Shannon's life. No, just because she sent an email. That said nothing. And that Shannon begged for.
This is just like last fall, when another one of the SN kids was overwhelmed with emotion because "I did it! I cooked an egg all by myself! I actually cooked an egg!" Making such a huge deal out of mundane things is not dignifiying SN people; it's highlighting their inadequacies.
And look how April seems to be flinching.
Panel 5: So I guess this is it. It's not about repercussions for letting RebeccaH cheat off her; it's about the contrast between RebeccaH and Shannon. And April is probably not going to establish a pattern of emailing Shannon; she's done her one good deed and that's it. So when April doesn't reply to Shannon's reply, Shannon will feel more rejected, because she was more elated before.
And furthermore, we've been here before. The mall sequence, remember? "I'll never be as pretty as Becky..." [hug from Shannon, who thinks April is "really cool"] "But some days...it's good to be me!" She doesn't like Shannon! She just likes to stroke her conscience! Die, pizza-face, die!