The time in Qarth has essentially revolved around getting money, ships and an army. I think the threats and the way in which she asks is relevant to her character. She was not raised as a noble, has no concept of how to "play the game" for lack of a better phrase. She is rather green to diplomacy as she was basically living under the wing of Viserys, then married to Khal Drogo, and only now has she taken any control.

It's a bit of immaturity, but its consistent with the character when you consider her predicament.

[In the show it has been slightly more tedious than the books albeit]