Millie does this too Gilly .. generally to her big red cushion .. she's never done it to either tris or me in any way - though I can understand the shock at seeing you daughter crawling round with Butty attached!!
quite disturbing!
Anyway - I never really had any thoughts on it... except it was her hormones and she'd grow out of it - we tend to snigger to ourselves when we catch her, but ignore her after that. I agree with Karen though about the "glazed" look .. you could call her and it was like she didn't hear you ... nothing new there then!!