She looks pretty good...
1) She needs to work on brush interference. Immediately prior to release, the right arm (for a rightie) brushes the front of the hip. In golf, it is called "keeping the elbow tucked in". Your DD's arm at release is several inches from her lower body at release. This will ultimately lead to all kinds of accuracy problems as she gets older.
2) IMHO, her arm should be straighter at 12. She has almost a 90 degree bend in her arm for the entire circle until release. I'm not at all certain that her arm straightens at release. Could you possibly shoot the video from the 3B side?
What is the best arm position related to locked out all the way to 90 degree bend?
On the brush interference. What could be causing the lack of BI? It almost appears she is leaning or falling away-this perhaps?
What are some drills she can do and cues to help her focus on keeping the elbow tight?
Shes a "why" student-what can I tell her is the benefits of BI besides accuracy.
What immediate feedback would she gain with better BI?
She is a great spin/movement pitcher.
Id like to see her go from 50 to 55 this year to keep pace with the competition and make her change of speeds more effective. Advice?