I would say I'm pretty sure she's not teething. It's awfully young. I mean, stranger things have happened I'm sure, but it would be surprising for her to get a tooth so soon, definitely not the norm. My son does play with his tongue a lot, and yes he is teething right now, but he always has. I would venture to say that it's more along the lines of just discovering her tongue or maybe she likes the noise it makes or the feeling it makes on her lips. Babies are funny and discover new things every day, so I wouldn't worry. If it continues you might give your doctor's office a call, it could be an ear infection, although probably unlikely with that as well, but being irritable and rubbing at her ears could be a sign of that.