You might have noticed that even your newborn baby used to smile. However that was not a real smile but just a reflex action. The real smile actually makes an appearance when babies are over 1 to 3 months old. The smile that you get now is the genuine, happy smile that is an expression of an emotion. Whenever you will smile at your baby your baby will also smile back with happiness.
What you need to know
When your kid sees you happy every time she smiles, she would be doing it more often as she wants to make you happy. Encourage your child to smile more by making silly face, animal voices, peekaboo game, etc.