Kat was used to looking at a room and seeing all the angles. (1.17)
Casing a room is pretty much hardwired into Kat's DNA. She can't go into a room without figuring out how to get in it and get out of it without being detected. No wonder she makes a good thief.
Kat had already passed for a Franciscan nun during a particularly difficult job in Vatican City. (1.67)
Pretending to be a nun—is nothing sacred? They're not just lying to museum directors now... they're lying to the Pope.
[Kat] found her passport. She flipped it open and saw the name Melanie O'Hara beside a picture of herself in a red wig. (3.64)
Kat has at least five alternate identities to rely upon. That's more than Lisbeth Salander. We're impressed.
"It's fall break [...] I wanted to see how you were doing." (4.16)
We guess it's not that hard to lie to a master thief if you're related to the guy. Kat's dad never suspects that Kat actually got kicked out of school. Maybe his lack of suspicion is actually a testament to Kat and her dad's strained relationship.
The best time to pull a con is when the weather should be changing—but isn't. People feel lucky. (6.1)
It seems that timing is a big factor in pulling off a successful con. You have to find a way to anticipate and control your mark's reactions.
"You had to use her to help you? Gabrielle!" (8.43)
While Kat isn't exactly happy that Hale deceived her, she's really mad when she finds out that Gabrielle was in on the game. Why does this lie make Kat so much angrier? What's with her and Gabrielle, anyway?
The lack of a name worried her. The presence of a girlfriend, [Kat] assured herself, did not. (11.8)
Kat is deceiving herself here. We get the feeling she'd be pretty bothered if Hale showed up with a girlfriend. A girlfriend who wasn't Kat, that is.
The downside of being a con artist is that it makes you very hard to con. Even if the lies you tell are to yourself. (15.28)
We're not sure if Kat does a good job of conning herself or not. She realizes that she can't be a "normal" girl in a "normal" boarding school, but she really seems to have convinced herself that she doesn't have a romantic attraction to Hale. Which doesn't seem true at all.
"Whatever we do not [...] we do without Uncle Eddie's blessing." (17.10)
Kat has to convince her relatives to deceive their Uncle Eddie. They'll pretty much be lying to him if they get off their butts and do anything. But maybe Eddie was deceiving Kat and co. with his lack of concern about the situation in order to get them to do the job. Would they have been able to pull it off if they had relied on Eddie's help?
[The guards] didn't, of course, see that the pictures were really of the positions of the cameras; that their paced steps were mapping out the dimensions of the perimeter wall. (18.11)
As we know from playing any video game where guards can barely see outside a 45-degree angle, guards are easy to deceive. Especially if you're just pretending to be a goofy teenager taking pictures of yourself. Everyone underestimates Kat and her crew.