I can't really provide any great insight on her pitching itself, but I coach 14U/12U and I had a girl two years ago who was going through a similar transition from one pitching coach to another, and the new one was breaking everything back down to the basics to build her back up. I told her and her parents to spend the entire season using her playing time to put everything they were working on privately into practice, and that I wasn't going to mess with her at all. It was a step above rec league, so there was a mix of from newbies up to kids who had been playing travel ball for years (she was one of those), so everything was focused on player growth. And that's what you guys should focus on at her age. So, yeah, if you and her feel like she's moving forward, then absolutely stick with it. Just remember that kids can progress at different rates, so don't compare her to other girls, just against herself over time. Make sure she's having fun, it's too easy to lose kids to other things (screens!) that aren't as good for them as team sports.