Well, I never got the "brooding" vibe. That is a good thing in my books.
Yeah I tried not to do that, not a big fan of Batman's broodiness myself or the involving kids in crime fighting bit hench why Cardinal is a robot in his teenaged years, and instead make her a character that is not 'perfect' like Batman supposedly is.
While she is book-smart she's not street smart, despite being worldly she is not too familiar with normal society. She also has high expectations for her fellow peers in high society and tries to be an example of that despite the fact that people like genderbent Lex Luthor who are in it for themselves. Another thing is that she's one of the few with influence who supports Mutant rights.
The reason she is hard on Robert Knight, noodle incident aside, is that she wants him to be a better person instead of the socially inept womanizer he is, though I could be wrong on the womanizer part. As such she tends to be naggy and hold some grudges at times. She doesn't like being underestimated and prefers to be treated with respect, hench why she has trouble getting along with Robert and Archestorm and prefers the company of Greg.
She can also be a bit over bearing and has a tendency to overwork herself, which is expected.
There's more I could talk about but the bottom line is I tried to veer away from the vengence and brooding part and guide it towards making her not perfect, idealistic, and slightly naive. Or womanly, I guess.