At some point they need to be accountable for their actions. Where are you comfortable drawing the line? 18? 20? 30?

17 is easily old enough to understand the ramifications of claiming someone assaulted you. There are plenty of abused people who DON'T lie about their kind stepmother assaulting them. Allowing this particular child to get off with no accountability means "affluenza kid" should be let off because of his shitty upbringing, and young teens who murder, assault people, and steal should be let off. I am sure many of them had abusive upbringing as well. I have no problem calling them assholes, just as I have no problem calling her one.

She, however, is not an irredeemable asshole and will hopefully come out of this a better person and no longer an asshole.

Their abusive upbringing can help inform us of WHY they are like that, and how we might help, but she is still an intelligent being who is easily old enough to have a conscience and empathy, and as such should be held accountable for her asshole actions. Now she can move on and grow, which won't happen if she is given a "get out of accountability free" card.