My 12 year old daughter talks to herself?

My 12 year old daughter is constantly talking to herself. It is as if she is having a conversation with other people. Sometimes she is so entranced in these "illusions" that she doesn't notice anyone around her. When I ask who she is talking with she says she is just pretending that she is in different situations, eg: that she lots of friends around and they are playing. It seems as if she does this far too often, maybe 20-30 times a day. The teachers haven't noticed this at school but when I asked her she said that she does do this at school and everyone else does too. I am concerned and I will be scheduling an appointment with a doctor. Does someone have any insight as to what I might expect? Note: Not sure if this is relevant but, my 3 year old son has just been diagnosed with Epilepsy from a frontal lobe abnormality.