Daughter has been struggling making contact playing 16/18u tourneys. She usually looks good in practice and in high school and 14u games. It is a mental thing a lot. It isnt just against overpowering pitchers.
There are a number of reasons. It helps with:
1. Letting the ball get deep in the zone Many (most?) try to hit the ball too far out towards the pitcher.
2. They have to stay inside the ball to go to the right side.
3. They learn not to drop the bat head on outside pitches, creating a slice.
4. They have to keep their eyes on the ball better than what they're used to, because they're doing something different.
I'm sure there may be better reasons but these are what comes to mind. Also, be aware that they will not like doing it until all of a sudden they are getting good right field gappers.
Also, don't let them get away with ground balls to the 2nd baseman. That will happen when they try to pull an outside pitch. And don't listen to the "that pitch was inside, I can't hit that to right field". It doesn't matter if they can or can't, trying to do it is what helps.
Lastly, a burpee for each hit that doesn't go to right field is a great motivator!
Mine had a slump at the beginning of the season, her first of her career. It was the end of the world. Just don't let her get down on herself and tell her to keep at it. There are examples of great hitters in softball and baseball that have it happen, so why can't a yound lady? All it took was one solid hit (deep fly out) and she started to go nuts with her bat again.
I would agree with you about the 16U mental thing too. She just needs to relax.