I struggled tremendously at that age. I was angry, moody, sad, happy, confused, etc, etc. It is a very, very tough age and being in middle school is not fun. Kids at that age are all going through the same thing and because they are miserable they make everyone else miserable too. As an adult I dont think if I were to go back to middle school today that I would survive. Kids are so mean.
You must take hormones into consideration. I would cry and blow up at my parents at nothing at all. One day (instead of yelling back at me or getting mad at me for being so out of control) my mom asked me, "what is wrong, why are you so angry?" She tells me that I told her that I didnt know. And it was an "I didnt know" meaning that I knew I was out of control and I didnt know why or how to stop it. It wasnt an attitude thing by saying I didnt know. I was lost and couldnt control myself or my anger.
I would have her talk to a therapist. She probably wont want to but it really helps to talk about problems, especially with someone who isnt involved and is nonjudgmental. I strongly suggest this. It shouldnt be as a punishment because she will just resist and it will make it harder for the therapist to help her make any progress if your daughter thinks she has to go because she's in trouble. If this is something you decide to do I would talk to her and say that you think it might help to have her talk to an adult who is "outside the box," knows how to deal with anger and emotions shes having that she may not know what to do with. Dont ask her if she wants to go, dont give her a choice. Tell her shes going for a while just to try it out. Make her go consistently for one month. Dont tell her how long the trial period is because she will probably resist until that time is up and say that it isnt helping because she doesnt want to go. Once a month for one week will be 4 times and your daughter should be more open to talking to a therapist after she has seen them several times. Keep in mind that it can take 3 months or a bit longer to see any results and to see results you have to be consistent with appointments as well as doing what the therapist suggests while youre at home.
So many parents think that if they send their kid to therapy that the therapist will "fix" their kid. The therapist is just a nonjudgmental coach who offers suggestions, insight, and ideas for the family. The real progress comes from what happens in the home. Consistency is key.
I hope this helps!!! Good luck and keep in mind that she doesnt know why she feels this way and why she is so angry and emotional. 11 is a very tough age, especially in today's world!