It is amazing to see your baby imitate faces back at you whenever you express an emotion to her. Little babies are capable of imitating the emotional expressions that they see on the faces of adults. If she sees you with a happy, sad, or angry expression, she will respond by mirroring that expression. This is because the part of her brain that has ‘mirror neurons’ has started developing.
Now, that your child has some control over the facial muscles, she is able to copy your expression. Your baby imitating facial expressions will be the highlight of your day. The way kids respond to the expression by copying them is a very important development process as it is the beginning of their emotional process and empathy towards others. If your baby doesn't imitate faces, don't worry she will begin to do the same in some time.