Oh bugger. Hmmm, it's not really common for kids to start at this age, so I don't have any great ideas for you. I'm trying to think what technique would work best, but as her mum, you will probably know better than anyone. She's a bright little thing, could you talk to her about it, and how it could hurt her teeth? And then remind her when you see her doing it? Buy her a special *something* to hold on to, instead of sucking her thumb? She doesn't get to do both, if she's sucking her thumb, the special thing gets taken away, etc. Um, tell her it's something that only babies do? (Though that would be a last resort for me).

Sorry babe, I'm racking my brains, but not coming up with alot!