I think that is the first step, a meeting with the teacher and perhaps she can encourage your DD to play with others kids. I know my sister teaches prep & they encourage them everyday to make new friends, by encouraging them to play together. In relation to the aggressiveness I don't know what to suggest but perhaps she is asserting herself b/c of past issues?? Not too sure on that one. I would talk to her though about what you saw and give her another suggestion how to ask the kids if she can be first because she just forgot to take her hat off.

Your daughter sounds like a perfectionist - she doesn't want o get things wrong or perhaps she has been embarassed before about making mistakes? I don't know what the solution is other than encouragement when she does attempt the word/task and make a massive deal when she does get it right on her own.

Best of luck