She has super-persuasion skills.
When Abby wants something, you can bet she's going to fight for it. In this episode, she wanted to move out of the basement to join the rest of her peers—displacing the accounting team in the process. Gibbs initially told her it wasn't going to happen, but she kept looking for new ways to convince him. The balloons were a very nice touch. He didn't go along at first, but her persistence paid off and Gibbs had another word with accounting.