It's probably nothing, and just the regular mind of a ten year old, but this is what my sister is like:

She has the most amazing imagination I've ever seen, she will go outside in the snow and just crawl on her hands and knees for hours on end, pretending she is an animal such as a polar bear, a tiger, a snake, a wolf, or anything. She always talks to her imaginary friends as if they were right there in front of her. I walked into her room once where she had her stuffed animals lined up and she was introducing them to her "friends from school". I asked her what she was doing. She said showing my friends my Webkinz (a kind of stuffed animals...). I said what friends? She said "They're sitting right there!" I was kind of confused and I said "You can see them?" she said "Yeaaaah..." In a tone that kind of said "What the hell is he, an idiot?" So I said okay... and I left the room.

Is this the regular ordinary mind of any ten year old girl? She has the most vivid imagination, she always talks to her imaginary friends like they are right there and she refers to them by name (Kelsey, Maddy, etc). And I mean always, she never is actually "alone".