Getting teeth

My baby is getting teeth, I mean, a tooth! It is so cute just peeking through on the bottom and oh so sharp! I'm not sure how much longer this nursing thing is going to go on now that there are teeth coming in. How do you teach a 7 month old not to bite? She is also starting to sit up better now. Can't sit up on her own completely but almost there! My baby is becoming a big girl too soon!