If you have been to all the lessons and watched and learned along with your DD, and IF DD will let you work with her, then I say save yourself the money and work with her your self.
I tell my students that unless they feel like they need a tuneup - we stop working together when their season begins. I feel this should be true of pitchers as well, but I am in the minority on that one....
Based on her age group...Once monthly for Batting if you feel it is needed. Supplement with personal work at home.
Fielding will work out fine as practices are rolling three times a week plus games and there will plenty of coaching support and reps on defense.
If it were younger I would say at least every other week.
Last night was great at her lesson. Her instructor was running really late do to helping at high school tryouts. While we were waiting, one of my daughter's team mates showed up to practice with her father. Now, my daughter is pretty much in awe of how good this girl is and was thrilled when she walked over and asked her if she wanted to practice with them. This is the first time I've really talked to this guy, but I had been told that he is an outstanding coach and helps out in the organization. Well, my daughter loved working with them and he was able to see instantly what she needed to work on. He only uses tees to warm up and then it's front toss or live pitching. After a half hour, they move to fielding drills etc...
When her instructor showed up, she actually asked him to come in and help out with the lesson- apparently he had helped her prior to going to College. Anyway, after the class was over, he came over and said his daughter really loved working with mine, and wanted to know if she would like to come once or twice a week to practice with her. ---wait for it.........FOR FREE! He said my DD will be a nightmare for pitchers if she can just get better use of her lower body instead of relying on her upper body strength.
It was very exciting for my daughter, and my wallet loved the news
Fortunately, he said he didn't want to mess too much with her swing, but get her to use her lower body better. I think it will be a good bonding experience for her with a team member also. 8 of the girls have been playing together for 4 years, so it might help her feel even more comfortable.