I know you talked about how Lise would react to an asshole in the Hogwarts Feedee/feeder group. How would Cressida react?
If this was pre her losing her humanity along with her first boyfriend, she’d probably just be like ‘meh that’s none of my business’ and look the other way. Cressida may have worked her way up from the bottom economically, but she has none of Lise’s sympathy for the underdog, and none of Lise’s righteous fury. To Cressida, it’s every man for himself. She’s still standing because she fought, and if someone else is in trouble, she’s not about to save them from drowning. To her, they oughta suffer like she did.
If it was after her first boyfriend’s death, when she was already being an asshole feeder herself, she’d probably give them helpful tips and pointers--how to gaslight someone, how to switch the labels on their clothes, sleight-of-hand techniques for slipping stuff into their food, helpful potion formulas, etc--in exchange, of course, for a nominal fee. Because all of Cressida’s motivations are essentially financial.