Changes and growing up...

As much as I hate my little girl growing up, it's going to happen.  She's been having aggressive moments at daycare and I'm not sure why.  I love my little girl.  I don't want her to be that bully we hear about in school.  Yesterday my daycare person said she was sitting on one of the older kids.  She's only a year behind and smaller than all the other kids.  The kids were screaming that G is sitting on M to the teacher.  I was so shocked.  What causes kids to act like this.  When I picked her up she slapped my face.  I told her no, we don't do that.  Then she rubbed my face.  I wonder if it's a growing spurt and she gets angry because she's hungry.  Daycare does time outs and so do we.  She's only 2 so we'll have to see how things happen but I'm keeping an eye on this aggressive behavior.  I don't like it and feel awful for the child she sat on.