"It doesn't matter what Avery did. It doesn't matter if she took Liam's toy or if she hit him, or even if she bit him first. "
Lady if this is what you are teaching your child then you are part of the problem. Yes, it does matter if she took her younger sibling's toy. Yes, it does matter if she bit him first. Telling her that her that she has no responsibility for  the consequences of her behaviour is a recipe for disaster. No wonder you are having flash-forwards to "flashes of our daughter at 19. Drinking too much and wearing a dress that will probably barely cover her body." It is what you are teaching her now that decides what her future behavior will be. Apparently you have already thrown up your hands to the idea of getting her not to drink excessively 16 years from now.
And this bit in particular "or even if she bit him first." you are telling her that she should be able to assault a man and expect not to be assaulted back.