schizophrenic?

Sorry to hear that. She is mentally unstable, but to conclude schizophrenia without further screening, shouldn't really hold any merit. First a doctor has to rule out other complications, like seizure disorders, metabolic disorders, thyroid disfunction, brain tumors, etc. Usually, people diagnosed with schizophrenia experience a combination of hallucinations/delusions, lack of emotions, and disorganized thoughts. This fits your neighbor's condition quite well. You also mentioned it's not in her family, but this isn't really that important because schizophrenia is multifactorial and can be epigenetic (i.e. if you have an identical twin, you could have it and your twin may not).

The first thing I was wondering was if she takes any medication because studies suggest that excessive activity of dopamine-releasing neurons in certain areas of the brain are associated with schizophrenia. As a result, drugs that block the production of dopamine, such as the dopamine antagonist chlorpromazine (Thorazine), sometimes help patients with schizophrenia. On the other hand, the drug amphetamine ("speed"), which stimulates dopamine release, can produce the same set of symptoms as schizophrenia.

The first thing I would recommend is have her see a doctor immeditely, she may even need to psychiatrically hospitalized for a little while and be treated with the right medication, otherwise you may need see her tomorrow. In the past, people with these conditions would simply be deemed (demonized) - it's sad, but true.

So she's 14 and she's been experiencing these symptoms since she was 10? Is she an intelligent girl, does she do well at school?

@Star  Yes, she has been admitted to a psychiatric hospital this evening. I've learned that she took Methylphenidate which increased these symptoms dramatically. She was immediately taken off the adhd medications but the voices did not go away.

@biology101 she is not "gifted” but she is very intelligent for her age. She is not lacking in any particular area. She has great social skills with adults and students her age. The timeline for hearing voices is a broad estimate. I think it may have occurred a little later around 11-12. She first referred to them as friends. She says they never told her to do anything harmful or bad. It’s the Methylphenidate which really has brought this to a level where she had to confront her mother. She was removed from them right away.

As biologist i could only recommend contact with psychiatry specialist. But as far as we know the only method of "therapy" is (a) administer psychoactive drugs, or (b) apply some kind of psychotherapy. But since she is 14 there is little possiblity of schizophrenia, because it manifest at later stage of life, especially at 18- up., so this is strange especially with that kind of symptoms. Also, psychoactive drugs have profound side-effects, giving them to developing children can be toxic and damaging. BUT the things like "voices" have also another explanation. My biology-side stops here, and neither psychiatrist nor neuroscientist will help much. Since the psychological phenomena are scientifically unexplained, (contrary to popular beliefs that they are simple determined
by neurons and their connectivity) i suggest to contact the exorcist. Seriously, i've seen some examples on my own eyes. Why not to try? From biological point of view this is non-invasive, and could classify as "psychoterapy". Strong autoagression and external "influence" is not very likely to happen in standard conditions. If qualified exorcist will tell that tis is psychological issue then simply go to "standard" psychologist and/or take drugs.

Could you tell us a little more about this?

Just wanted to add, treating is somewhat trial and error. It could take several months to find the right medication, dose, combination that will work for her. It won't be an easy road, but sounds to be on the right track.