Now, despite her fierce nature, Mira's normal neutral attitude is quite that of an aloof and cool girl, when it comes to enemies, she becomes pretty much indifferent and well, with allies and close ones you have seen how her cold façade melts away to reveal her warm inner self, Aster finds her quite cute which is why he likes to tease her.
But, there are two things that can actually make the ligress girl become quite aggressive, the first one is normal, despicable acts aren't liked by any decent person after all, Xander and Kyle fell in this category given that they were actively targeting Kana, and you saw how Mira was planning to rip them to shreds.
Even so, that angered ligress still remained composed, she simply had some "trash" to clean and got a bit heated due to it, that's all, however the second thing that can bring out Mira's aggressiveness, is personal.
