well, the question is "WHY?". "Why are you a bad friend?" In Mandy's case.... the incident with Claire was a result of Mandy having a control freak moment and going nuclear over Claire doing the same thing Claire does every day.... and trying to force Claire to well... stop being Claire. More specifically, Claire's habit of taking selfies for literally everything. Mandy freaked out about it because when Mandy invited Claire to study at Starfire's house... Claire's daily selfie regimen included Starfire and the Teen Titans. Not because Claire even went looking for them.... they just happened to be in the room.... like all of the living room, and just kinda hanging out with Starfire. and Mandy lost her mind over the fact that Claire isn't into Mandy's shtick of acting like she hates Starfire.