L.C.
C.,
I also have an almost 10 year old. She'll be 10 in September. To be honest at first I was going to say hormones. But as you described her behavior, I think it could be more. Maybe something is going on at school. You need to sit down and talk with her, because, believe me, even at that age they start pushing drugs and everything. So, maybe have a mommy and me day, do some shopping, have lunch out, and really talk! It's a less formal environment, and I know my daughter open up to me better when it doesn't seem like I'm making her.
I wish the best!
L.