It is not to early for her period to start, (especially with all the hormones they put in our meats!!!), so that could possibly be it. Maybe you should make some special time with her take her shopping and see if she will open up a little to you, (with my children I would get more attitude, and then they would open up). She is also a pre-teen, her own hormones are doing things to her that she may not even understand. I am now going through this with my 8 year old son, I thought it was too early for him also but everyone deals with things differently. When I notice he is getting nasty, (usually when his 4 year old sister will not leave him alone), I try to do something to distract her so he can have his private time and it does seem to work, I think he just feels over-loaded, like I do after a hard day at work). Just be there for her, and I know it sounds harsh, but... she is only 11, and YOU are in charge so if somethings you try dont work, and she feels like she is getting the upper hand with her attitude, she will take advantage. So you have to be careful in that respect also. I hope my rambling helped, good luck. By the way I have 5 children ages 21, 19, 18, 8, and 4, all girls except my 8 year old, and I still have my hair, (grey, but I still have it). GOOD LUCK and keep your patience.