What a Pettyprincess she is! (No offence DPrincess, haha) But seriously, she's just being a jerk because you fired her. Can you get them out sooner? If it were me I would let everything roll off my back for the next week until they are done and let her know that her petty tricks don't bother me. If you let her see she's making you mad then she will feel like she has taken the power, know what I mean? Some people always want to be the most powerful, etc.