Here is my two cents...
Teenagers are now trying to find that balance between indepedence and relying on their parents. Friends opinions and what other people think of them has become a priority. If a boy looked at her funny, or her friends stabbed her in the back it is going to affect her. They are at that stage where they want to deal with their own problems and not have to run to mom and dad all the time. As much as it pains parents to not be able to stop their kid from being hurt, or being upset, they are learning to cope and deal with it on their own. Another thing to keep in mind is priorities can change. Not that she doesn't love pitching or she wants to quit, but sometimes when you have a lesson scheduled one of her friends asked her to go shopping with her, and she would really like to go shop. Flexibility and choice work well here. If you say "you probably need to throw three times this week, you pick the days" she can plan it around her social life as well and not feel like softball is the only thing in her life.
Sometimes parents forget they are kids too. It is ok for her to say dad/mom I don't want to pitch tonight. She is allowed to take the night off, or skip a workout here or there. This does not make her love the game less, or want to be the best any less, but remember her body is changing and it's possible to be worn out, or just exhausted one day. Hormones fluctuate and cause moods, which could be part of the reason she is hot and cold or split personality.
Believe me, I know that cramps or PMS are not valid excuses not to play, and coaches aren't going to hear it. Girls have to learn to play through the discomfort and I am not trying to make that excuse for them.
My suggestion is take interest in other parts of her life (I have no idea if you do or not, and I am not accusing anyone of just caring about softball. Please don't take it that way) There are so many great parents here! Sometimes instead of a workout, go for ice cream or something and just talk (not about softball) and most of us know that when travel ball starts, social life stops with their school friends (unless their school has a travel team). Encourage that social life and for them to be involved in things other than softball so she gets away and has a break.
As you said, you aren't alone! Sorry this is very long winded!!