I'd be surprised if Kara were evil enough to deserve whatever the Black Void have in store for her. Being a criminal only means she's breaking laws, which may or may not be "legit" laws; for example, Luke Skywalker was a huge criminal (and a terrorist), but he was no villain.
Even if she is a genuine crook, does she deserve what the Black Void will do to her? Not knowing the extant of her crookedness and what the Black Void plans for her, it's hard to say, but I'd lean towards "no".
Maybe Shade is being forced into accepting this job, I don't know. But right now though it looks like she willingly accepted a job from some extremely evil people, which would make her a villain.
At this point in time, unless I were specifically playing a villainous character, I'd always help Kara over Shade. You get extra weapons that way, too, which makes it an even easier choice.