As someone who has been around Pattar a bunch-that is a gross mischaricterization and a little out of line.
I have a DD who pitches in 12u, so does my opinion count since it's a 12u pitcher in question? Losing focus, falling apart, having mechanical break downs, etc are all par for the course and understandable. Pouting or fit throwing are not (they aren't acceptable at school or at the grocery store, why would they be acceptable anywhere else?). He was pretty clear in that he was stating that IF that's what OP's DD was doing, then it should maybe be addressed but that if it was other stuff that it's probably normal 11 year old girl stuff and would take care of itself.
I agree with this completely. My DD currently pitches in college. We have been through everything from teeball (obviously she didn't pitch there ) to women's league softball, and every place in between. When she was 9 or 10, situations like the OP is describing were commonplace. She wanted to win, but she really didn't care one way or the other. She was in it for the fun more than anything else. At 11 I started to see a change. The lack of dedication from her rec ball teammates started to bother her. If they started making errors behind her, she tried to be too perfect and would lose her accuracy. Ultimately this is one reason she chose to move to travel ball. She didn't play travel prior to that because she wasn't interested. But once she got a taste and realized there were other girls out there just as interested as her, she was hooked. Gradually as she got older, she started to learn how to deal with adversity. Eventually she got to the point where is seemed as though nothing bothered her at all. One coach used to call her "ice cube". Another "bull dog". She didn't care for either nickname but appreciated the sentiment. In high school she was the only travel ball player on a team that played against travel filled teams. It was ugly to watch, but she always had a good attitude about it. The coach at one of her top college choices wanted to come see her high school team play. She warned her in advance that her high school team wasn't very good. The college coach came anyway. After losing by 3 runs to a team that was immensely better than them, the college coach could not stop saying how impressed she was with DD's attitude and leadership. She was offered a spot that night. Ultimately she turned it down and plays for a different school, but it is still a moment she talks about often.
To the OP. At 11, she is still very young and VERY early on this journey. This may just be part of growing up for her. I wouldn't worry about it too much at this point. But as she gets older, she should start working out of it. Dealing with adversity is something we all have to deal with in life outside of sports, and it is one of the greatest aspects of playing sports. Some never learn how to deal with it and ultimately leave sports because of it. Some will learn to cope with it. Some will be motivated by it. As a parent, it is your job to help her learn her way. Guide her, but don't force it. Good luck.