They didn't really justify that very well. So she met her thief father and now suddenly she loves all thieves even though she has spent her entire life hating them/working against them?
shareShe forged documents and clearly was excited by / idolised the greatest thieves. You didn't pay attention to her character well enough to that point to ascertain her true moral compass.
shareBecause it was lazily done is the problem. Her character is so erratic that nothing she does makes sense and she's just kind of there to do things as the plot necessitates.
-I'm by the book and going to get you
-oh I still love you
-I'm coming after you by faking forms assuming nobody will ever notice
-oh someone noticed? Guess I'll just disappear forever then and assume nothing will ever come of it
She forged the documents because she was so determined to stop the thieves, not join them. It never once said or implied that she idolized the greatest thieves. Did we watch the same movie? Yes she knew about and discussed them sometimes, but that's part of her job. She hated all thieves and made that quite clear... until she decided to throw her life away for no legit reason.
shareIt is implied she sort of idolized the art of stealing when she was younger (they say something like "her father taught her everything he knew"), but then her mother lied to her about her father dying in jail. From then on, she took a vengeance against crime because in her head, a life of crime is what killed her father.
Then, once she realized her dad was still alive, it changed everything. Plus, she was most likely going to be fired from her job for forging documents.
Because, in the end, she reverted back to being Catherine Zeta Jones hanging out with her celebrity friends... screw the plot! ;)
shareAs someone mentioned above, she very clearly admired great thieves (like LeMarque, the guy who lifted the house, etc.) even while she viewed herself as on the side of the law. (It could be pointed out that it takes a lot of cleverness to catch a thief, too, so she probably considered it a match of wits.)
She also was mad at Rusty (and his thief friends, by extension) because he had left without telling her who he really was, assuming that she wouldn't love him any more. She did still love Rusty, and her father, even though they were thieves, but she had been hurt by them. Trying to catch Rusty was kind of a "getting even" thing.
However, in her pursuit of catching Rusty, she was totally okay with bending the rules herself, which shows that she was no straight arrow herself. In the end, her love of her father, and the fact that, because she had ruined her career by forging documents while the thieves still got away, led her to stay with Rusty.
It's not perfect, but the lines are all there.