Night time talking

Hello. I work Night shift, so on my nights off I'm normally up until around 3:00 AM. I have two small children, they share a room for now. My son sleeps all night, but my daughter is up almost every night. That doesn't bother me but she starts talking. She says things like "let go" "Go away I'm sleeping" it seem just like shes talking to some one. I check on her and she looks at me not seeming in distress and says "Hi daddy I'm sleeping." I guess my question is is this just ramblings of a 2 year old or could there be something interacting with her In the night?