"that's so mean..."

I am in need of some serious seasoned advice OR pitty :). My sweet 23 lb 2 year old, who says things like "how you doing today?, you good?" Or "ummm I would lie a blue popsicle please.." Is terrorizing the kids at school. All of the sudden she is pushing, fit throwing, and worst of all BITING. She is by far the smallest, but is doing some damage. I have no idea what to do. She is so good in public, follows instuctions easily, and really enjoys to play. I'm concerned that there isn't enough structure in her room or that she is frustrated. I'm really stressing about this. We've talked to her... Got on to her... You name it. Tomorrow we are going to try rewards for increments of time with good behavior, who knows. I'm trying to stay positive!

I've repeated the same phrase to her about biting, now when you ask her about it she says "thats soo mean, I won't do it ever again" yet tada! I pick her up and she did it again...