Is she doing this as a recreational activity (being with friends, just for the fun of it, etc.) or does she have goals set for improvement? Both fall ball and indoor can be either, it just depends on what you want to get out of it.
I have no idea what level of play she is now, or what level she has goals for. If she is determined to "be the best she can be" I would assume she has a qualified instructor. During lessons with her instructor, she can be shown the specifics of the mechanics of different pitches, different ways to get better spin, mental approach, and much more. Then, a great venue to "test" those things is a relaxed game atmosphere, such as fall ball and indoor. It's the simple concept of "teach, assess, correct". A weekly lesson, followed by practice and self assessment. Go back to her instructor with feedback on how things are working out. She can even keep a little diary at each indoor session to help jog her memory at her next lesson. Have her set realistic goals for herself during this time, with the help of her instructor.
You will be amazed at how fast she progresses when you approach it with a plan and goals!
