12 year old is the oldest of three and the most immature. She gets great grades in school but is socially awkward and has no friends. She is often rude to her siblings and very argumentative with her father and me. She is very immature when she plays often acting more like a 6 year old than a 12 year old which just comes off as obnoxious. I know I've failed to discipline her properly but I'm wondering, is it too late? And if not, how do you recommend I start?