Caper Rationalization: Anna had nowhere to go when she came of age, and since she has no exceptional skills or physical prowess, thievery was the only thing Anna could turn to.
Doorstop Baby: Anna was left at the doorstop of an orphanage, thus she doesn't have a last name.
Karmic Thief: Anna was only going to steal three coins from Elsa's purse, noting that it was literal pennies to a member of nobility.
Living Lie Detector: Elsa claims that she has this power, when really she made this up so that Anna wouldn't try lying.
Mugging the Monster: If she knew that it was Elsa she was robbing from, it is unlikely she would have attempted the robbery in the first place.
Wouldn't Hit a Girl: Anna makes a point that she wouldn't hurt an innocent woman.