Last year my daughter's team made it to regionals. They used one pitcher the majority of the time, but had a couple others that picked up a few innings here and there. I would guess the #1 pitcher threw 90% or better of the total innings played.
Pitching is an area all schools try to develop as many ladies as they can but realistically for most schools they have one that gets the majority of innings and a second that may start a handful of games vs. weaker competition..
If they are lucky teams may have one lady on JV that may be able to get varsity innings and a position player that can throw a few innings.