I would suggest that you look for information on central auditory processing disorder. this is exactly how I behaved as a child. It haunted me throughout my life. If she has this disorder, you will need to know so that modifications and considerations can be made. You can find info on CAPD at my web site.
www.geocities.com/denisev2/
Dear Stephanie,
It sounds like your daughter requires a good amount of structure and supervision right now in social situations. The shyness needn't be addressed in any way other than by offering encouragement and support. The aggressive behavior needs to be interrupted and she should be timed out immediately on the occasion of any such behavior. In order to do this, of course, you need to have close adult supervision so the behavior can be handled. Of course, with a child so young, play should be supervised closely in any case. Don't give up on your daughter. She's at an age when she's learning about relationships and interaction. She'll do better as time goes on and she matures. Be patient.