Drea's revenge against Erica and her little sidekick is a little disproportionate, framing them for doing drugs and ruining their lives. It is likely from all the pent-up anger at Max and her former friends.
Obviously Eleanor's primal scream when she's driving Drea home is meant to be for comedy, but the timing makes a lot of sense too. Initially, we think that Eleanor is frustrated that the girl who outed her turned out to also be queer. As we later hear, Eleanor hoped that Drea would realize the story Eleanor tells about Carissa was really about her and that she'd get some kind of apology. When Drea doesn't and instead makes a quip about "getting outted by your own team", it's no surprise that Eleanor snaps a little bit.
Eleanor's cruelty towards Drea after she learns her true identity may be in part due to her blaming Drea for indirectly causing Gabbi to break up with her.
She may also be taking her anger out on the rest of the school for causing her argument with Drea which led to Gabbi breaking up with her, and possibly taking a measure of revenge against Gabbi herself by disgracing her brother Max.
In a way, Max and Carissa were lucky they had true scandals to leak out. If not, Drea may have had to resort to more cruel methods such as planting drugs on them like she did Erica, or worse.
Some of the texts between Max and his girlfriends include underwear-clad pictures of the latter, making it even more humiliating when Drea and Eleanor leaked them out. There is also the possibility that Max was planning to leak the photos out himself or use them as blackmail material.
