I am going to add my 2 cents here but keep in mind this is not a steadfast rule and variations occur based on the physical development of each individual girl. This is my base pitch count for practices and games based on practicing every other day and encouraging other activities to maintain balanced muscle development. Now, not counting warmup and cool down throws:
8 and under = up to 30 pitches
9 - 10 = 35 - 40 pitches
11 - 12 = 40 - 50 pitches
13 - 14 = 50 - 60 pitches
15 - 16 = 60 - 75 pitches
17 - 18 = 75 - 90 pitches
19 and up = 100 - 120 pitches
If she is working primarily breaking pitches I will scale this down a bit for those under 18.
Hope this helps give you a starting point.
8 and under = up to 30 pitches
9 - 10 = 35 - 40 pitches
11 - 12 = 40 - 50 pitches
13 - 14 = 50 - 60 pitches
15 - 16 = 60 - 75 pitches
17 - 18 = 75 - 90 pitches
19 and up = 100 - 120 pitches
If she is working primarily breaking pitches I will scale this down a bit for those under 18.
Hope this helps give you a starting point.