I wish more young ladies would speak up for themselves.
We have also by and large faced many situations where a coach has instructed our daughter to do something in warmups or practice that goes against what she has ben taught. The most effective way to deal with this to avoid drama is to have her simply say that she is being taught some specific things by her PC and ask if it is OK to follow her normal routine for team warmups. Few coaches are going to force a kid to do something if they ask nicely. If you do run into a megalomaniac who insists things are done his way then you can politely step in and request that since her PC is saying one thing, that you do not want to confuse her by doing it differently in practice. If they still are a jerk then draw a firmer line. Then there is always the smile and nod.
...her team coach - right after he had opened with "I'm going to change your fast ball motion tonight" ...