IdC and Sacrifice aside, I don't think many people in the DCU realize that anyone on the Justice League is ever less than 100% boyscout. The villains especially, since their perspective on morality is already skewed. "She's a hero, she'd never do petty vengeance" would be a pretty common assumption for a villain to make, in total ignorance of the fact that Zee's a Vertigo hero.
I mean, it makes less sense considering Ivy explicitly references the Selina mindwipe here, but I can see it being just a matter of habit (both Ivy's and Dini's as a writer) to treat a hero like someone above doing something nasty and therefore not take that possibility into consideration.