So, I go out to the ball park and I see parents struggling with their DDs in the circle. They are making themselves and their DDs a nervous wreck. This advice is for any advanced pitcher.
Here are two things to understand:
1) When your DD is pitching in HS and is "good", she almost certainly knows more about pitching than you, the parent, do. She is in the circle. She sees the batters. She is working with the umpire, the catcher, and the coach. She knows which pitchers are working and which are not. Therefore, any advice that you might give her is likely stupid. It would be like her walking onto your job site and telling you how to do your job.
2) One of your DD's job is to "be a leader". News flash: Teenage girls will not respect her or follow her if Daddy is giving advice from the stands. Worse yet, if Daddy comes into the dugout, it is the kiss of death. Getting advice from Daddy in front of her friends is akin to your DD taking her teddy bear to her HS classes.
How should you conduct yourself?
1) Sit yourself as far away from the action as you can.,,preferably down the 3B or 1B line past the bases. Why? You are, inevitably, going to groan or sigh...you are, after all, only human. This minimizes the chance that your insane mumblings will be heard by anyone.
2) You can make mental notes about the strategy behind pitching and discuss that with her at some later date.
For me personally, I spent her sophomore, junior and senior years down the left field line. I did give her advice after the game. Here is the advice that was most helpful to her:
a) If your breaking pitch isn't working, grab the backup catcher and work on it between innings.
b) You have to throw your breaking pitch/offspeed pitch even if it isn't working. You cannot abandon a pitch simply because you couldn't get it to work in your first 10 pitches.
c) Learn the umpire's strike zone.