Disagree.
DD is one player. She can only affect the team as much as the coach allows. If she is hurting the team, the coach has the ultimate recourse...riding the pine. The rest of the team can follow the coach's directives.
On the other hand, the coach affects everyone...and not just the current players. As 2016 recruiting results demonstrate, the coach is the one person in a position to impact the team for years to come. You think recruits turned down UT because of Diamond DeShields? Especially when she hadn't played a single game at UT yet?
Diamond isn't paid to run the team. Holly is. If CHW can't handle Diamond, she doesn't need to be coaching. Either play her or sit her.
Consider the possibilities and upside/downside to keeping each.
Is there a possibility that a new coach could harness DD's talent & make her a valuable asset? Worst case scenario if that doesn't happen...you have a sulky player sitting on the bench (not great for team chemistry but good teams have dealt with worse. I'm sure UCONN has dealt with prima donnas and still been successful).
On the other hand, do you really expect CHW to suddenly become a stellar strategic coach? That she will suddenly learn everything that she hasn't learned in 30+ years on the bench as head assistant and now head coach? That she will insert the right lineups, use timeouts wisely, restore team confidence in themselves, each other, & the staff, actually install a real offense, and repair any hurt feelings with players? And...in addition...top recruits will suddenly come knocking to play for her?
Personally, I'd bet on the former with DD as being more likely than the latter with CHW. You can probably find lots of instances in which players have turned around careers (especially with new coaches), but it's rare to find a coach suddenly being rejuvenated and transposed late in their career (without changing schools).