Split Personality?

Natalie has a cousin on my side who is six weeks older than she and is named Linnea. One day Natalie pointed to the girl in the mirror and said it was Linnea she was looking at. She loved to show Linnea how to brush her teeth. I encouraged this, of course, because it was so cute. Later, however, Natalie did something naughty and said it was Linnea who had done it, pointing to her left hand. Now, the entire left side of her body is Linnea - and she has NEVER mixed up which side it is. The other day she came up to me and said, "Mom, Linnea has some eye-wax," rubbing her left eye. Today she came crying saying, "Mom! Linnea hit me!" I told her to ask Linnea to please play nicely, and that comforted her. If my husband wasn't already a psychiatrist, I might be asking you all if I should be worried! My sister and I sure get a kick out of this, but I do hope it doesn't last too far into her childhood!