DD (5) is always chewing on something, whether it be a hairband, hairclip, a piece of string or a bracelet - basically anything in her hand goes in her mouth. She also sucks her thumb a lot. My constant nagging her about it is clearly not helping. We have tried reward charts, stern chats and constant reminders to no avail.
She is a very happy child who loves school and has lots of friends.
Should I just leave her to it and hope she gets bored of it one day?