Well my reasoning for putting Azula in that spot is her functions Ni (Introverted Intuition) and secondary function Te (Extraverted Thinking). Ni functions allow a person to see the possibilities in the world around them and develop on point responses to problems with rather unique solutions. This is Azula's specialty. She is a MASTER at adaptation and it's nearly impossible to catch her with something that she hasn't already planned for. Her secondary function is Te which allows a person to dictate which decisions are going to overall assist them in achieving their overall goal. Ni produces evaluations and Te encourages diagnoses which are never-ending cycles for INTJs. Having this process often helps them focus on what they really want and so their self-confidence in their positive diagnosis and analysis leads them to do whatever it takes to make it happen INCLUDING taking the appearance of being fueled by external forces which is far from the truth. Everything is just a piece of the master plan to INTJs.
So yeah... She's definitely introverted. That was one of the easiest to categorize for me. Hope this helps you.