Regarding her hostility towards the Alexander's, expressed in Tweets blaming them for destroying his reputation, dragging him through his own blood,etc. first, keep in mind that this whole abuse story never entered her mind until two years after she was arrested. The reason she latched onto it in the first place is because it's the one strategy that gave her any kind of advantage in the situation she found herself in by that time. When she was claiming she wasn't there, and then that the Ninja's did it, there was no mention of an abusive Travis, in fact she was all praise for him, and since that was the truth, by attaching her story to it, it lent credence to her entire lie, but when all of that didn't work, she again stepped away from responsibility in the only way available; she did it, but in self-defense, he was abusive, so she needed to defend herself.
Back to why she's sending hurtful messages about the Alexander's. First, it supports her whole abuse lie, but more importantly in her mind they are trying to hurt her, and she can't permit herself not to gain the advantage by hurting them even more. Never mind that the way they are trying to hurt her is by insisting she take responsibility for her actions, or insisting that the truth is other than her lie (which it is). The truth of it is meaningless to her, being in the dominant position, being believed over all others, is the only thing important to her, and she will attack anything that threatens that position, not that she actually holds that position in anything other than her own mind, and in those who choose to pretend along with her.