League pitching limits. A player can pitch a
maximum of 4 innings in a game.
This is in the league rules for 10u girls in PHBSA. Although it is not travel ball it is a very competitive league.
The one thing that most pitching instructors will tell you is take time off, usually @ a month, no practice or games. Most will tell you to do this after tryouts.
Let her pitch as much as she wants if she is with a good pitching instructor. One who has your daughters health as the top priority and you listen to their advise.
The problem with handling pitching limits in this manner is that you take the competitive spirit out of the hands of the pitcher. You want your pitcher to learn "how to win" from a young age. By forcing them to split innings with another pitcher - even when they are doing their best - you pull the rug from under them! A kid also has to know that the game is "on their shoulders" - that's what competition is all about!! If that's too much pressure, they probably shouldn't be in the circle.
For starters, the number of innings pitched has no relationship with pitch count. 4 innings could equal anywhere from 12 pitches (perfect game) to 112 pitches!! If the purpose of a rule is to limit pitch count over a certain period of time... well, COUNT THE DARN PITCHES!! Most youth league baseball orgs. now do it this way. As soon as the pitch limit is reached, they finish the current batter, then that pitcher is done for that period.
Freshman year in high school, (if I remember correctly) I set a limit of around 75 pitches for my 14 yr. old son, followed by a minimum 2 days rest. The coach knew that, and he was looking for the relief pitcher if he reached that limit. For fastpitch, I never had a limit on my DD. She generally averaged 80 - 100 pitches per game, with an average of 2 games/day during tournaments. There were times at 16u when her co-pitcher was injured that we stretched that a little at showcase tournaments, but that was not the norm. She usually got "jelly legs" before her arm/shoulder got sore. 18u through college, she noticed more forearm soreness from more emphasis on spins.
Bottom line is follow what your DD is telling you - body English included. Sure, she may not verbally complain when she's very young because she's being obedient and pleasing Dad. Every kid is built different - some are workhorses with great mechanics, while others are a tad frail and their bodies are more susceptible to repetitive motion injury. As a parent, YOU MUST be honest with yourself for the benefit of your daughter. Every pitcher should have a certified sports-specific trainer/PT professional, AND a physician who is very familiar with her sports activities. Any signs of lasting pain is a sign that something is wrong, and must be checked by one of these professionals.