The problem: Runs scored in the 1st inning count just as much as runs scored in the 7th. The pitcher has to give 100% from the very first pitch to the very last pitch.It's been suggested we don't have conversations about holding anything back in the tank (moderation) and instead work on endurance. As an endurance cyclists, moderation is everything, so this was surprising for me to hear.
Pitching is quite different from long distance running and cycling. (I road bike.) Pitching is much more akin to weight lifting.
Pitching requires 100% effort explosive effort for about one second, and then there is a period of two or three minutes of rest, and then everything is done over again.
Breathing is extremely important. There are various resources on the internet about breathing for pitching, but basically it is a deep inhale followed by a big exhale when the ball is released. Again, very similar to weight lifting.
Your DD also need to learn how to relax and rest between pitches. Odicci Alexander of JMU was a master at resting between pitches...watch her a little.
Around 15YOA, my DD practices were 1 hour to 1.5 hours long. We would do some drills, long tosses, and then work on speed/control/movement. At the end of the practice, she would throw 100 pitches. So, she was throwing well over 300 times in an hour.