The reason your baby is obsessed is that it is natural to her. If you watch a litter of babies with their mom, they are constantly sniffing and licking her mouth. The smells/tastes let them know what is good/safe to eat, etc. Your baby is viewing you as her mom. When I took in a tiny orphan boy, I had to teach him what to eat by putting it in my mouth first...before this if I offered him anything he would take a tiny nibble and then stop (a cookie! can you believe it?), once it was in my mouth once, he devoured it. He learned from his Human Mom.