Don't worry it's pretty normal I think. I teach 5 year olds and they often bite even at that age when they are excited as a way of expressing themselves. Even at that older age they don't have the cognitive ability to understand how to express excitement or anger. You could try to divert the excitement with a clap like the previous comment said - but she will grow out of it eventually Make sure she knows she doesn't get attention for bad behaviour - only good behaviour... It's a hard one though. Good luck to you!