It is difficult to know what is happening with your daughter. The obvious concern is that she is experiencing a serious psychological issue.
Psychosis in children is very rare. Psychotic symptoms typically don’t occur in a vacuum. Other symptoms often associated with psychosis in children include: delayed developmental milestones, poor motor function, language and speech problems, and poor academic achievement.
One possible explanation for the voices is that she is having imaginary conversations. Many young children have imaginary friends. They fully believe they are having real conversations and interactions with those individuals. It is not unusual.
A second explanation may be that she is experiencing a medical problem which is causing her to hear voices.
From a paranormal perspective, some believe that children are highly sensitive to the spirit world. There are many reported cases of children who claim to be interacting with spirits. In addition, individuals who claim to be psychic often report being first contacted by the spirit world as young children. There is no scientific evidence. It is impossible to confirm or deny the accuracy or honesty of these claims.
Before you can understand why such an event is occurring it is imperative that you understand what is occurring. The first step in this process is to have her evaluated by a pediatrician and possibly a psychiatrist or a neurologist. In addition, I would also recommend discussing your concerns with school officials. Perhaps they can help with a referral or they can provide additional resources. I wish you the best of luck. Please take care.