my niece has done this ever since she had hair and it gets that bad her fingers actually get stuck in her hair :S. she is now 6 so its been going on for a while. There is nothing wrong with her its just a habit. She does it alot when she is tired or bored. She is a real girly girl and i told her that if she twirled it too much then her hair wouldnt grow and then it would turn blue. Oh she believed me and my sister said as soon as she realises what shes doing she stop coz as she says "oh mummy, i dont want blue hair". lol im a meany i know.