Does she have a pitching coach? She looks athletic, and also probably has some speed going for her. I would work on her posture, to keep her from falling off to the left. Maybe someone can slow the video down and I can give more advice.
Amy, she's very athletic and throws hard for a 12 year old. I think she's trying too hard to get in that reverse posture, and it seems to me that it's causing her to fall back. I don't know how to slow it down without actually being in coach's eye. She developed a leap late in the season and got called once for it at PGF Nationals. When I explained to her that she should be dragging her back foot even before landing the front foot, she really took care of 99% of the leap. She does have a pc, but I'm looking for fresh eyes as well!
Yes. She is trying too hard and is probably imitating someone else. I would want to tell her "baby steps." She is losing some momentum, by being so tight through the shoulders, and scooting her rear end out towards the fence. I can't tell if she has a locked elbow or not.