When we first witness a meeting between Gabrielle and Kat, we see that Kat bristles immediately. You can practically see the jealously coming off of her in hot, green waves. She describes Gabrielle as "taller, curvier, and just in general more" (8.15). Talk about an inferiority complex, Kat.
Kat seems surprised when Gabrielle gets her act together and puts on professional airs. Kat observes:
There was no doubt in her voice. No flirt. No ditz. She was in every way Uncle Eddie's great-niece. A pro. A con. A thief. (8.51)
But we never see the flirty or ditzy side of Gabrielle unless she's putting on these personality traits for a job—say, to fool a male security guard. We have to wonder if Gabrielle really is flirty or ditzy at times, or whether Kat just says she is to make herself feel better.
Kat isn't without sympathy toward Gabrielle, though. She understands that Gabrielle's mother has been married more times than Angelina Jolie has adopted kids, and Gabrielle "had been trained to call five different men daddy" (8.49). That has to be hard on a girl, especially in a book where home and the family are two of the dominant themes (see our "Themes" Section for more on these issues).
If we were trained thieves, we'd want Gabrielle on her side. The curvy vixen is a valuable member of any thieving team, especially one who has a good head on her shoulders, like Gabrielle. But, um, if a famous painting goes missing while you're reading this, we swear we had nothing to do with it.