I've noticed it the past couple of weeks. She's also become very emotional, crying about silly things for no reason. At her friends birthday party she started crying because her friend said she loves ponies, my dd wailed "She loves ponies more than me". 
I'm a bit concerned that she might be starting peuberty very early. She's very big for her age, she's the hight of a 9 year old and weighs nearly 5 stone.
Should I take her to see the doctor, or is it nothing to worry about?