Hi exir, sorry for the long post.
I'm a child psychiatrist, and the only thing slightly off so far about your post is that psychologists have psychology degrees and tend to be therapists. Psychiatrists have medical degrees and tend to take the lead in treating mental illness. Psychologists can't prescribe medication
You're painting a picture that would ring true with me. Every presentation is unique so you don't have to be able to medicalise every single aspect of your child's world. Not only is she experiencing symptoms, she will be trying to make sense of them in a way that fits with what she already knows about the world. She also has a whole raft of defence mechanisms she'll use to protect herself when things seem overwhelming.
8 year old girl, is preoccupied with making stuff out of cardboard boxes. She sees wacky and weird things that aren't there (hallucinations), and seems to believe that she can somehow "build" the world around her by making a miniature world of her own using cardboard (is it correct to label that as a delusion?? Or still considered a hallucination?)
Your girl is experiencing both hallucinations and a secondary delsuion that is slightly grandiose
A hallucination is purely sensory, but people do try to make sense of what they see or hear. Thinking that she can influence the world is a logical secondary delusion if she sees the world as being made of cardboard. A secondary delusion is one that has a logical link to something. A primary delsuion doesn't (e.g. my pen is green so my parents are trying to kill me) The world is made of cardboard so I can change it by playing with cardboard is logical.
My biggest thought is about your descripion of the hallucinations. and this is in part becuase most hallucinations only involve one of the five senses. Most visual hallucinations are silent, most auditory hallucinations are invisible. You can't touch them, or smell them or taste them. They also tend not to last very long, they come and go. This is going to be your biggest challange if many things in her world appear solid. What happens if she tries to touch them?
You can get around this by linking the hallucinations to real objects, i.e. making a real table look like it's cardboard and appear to rip, but if the whole table is a hallucination then your child's hand should pass right through it.
To have your girl exist in this world you're going to have to blend together her symptoms, her interpretation of them and her imagaination, but this is what would probably happen. In this way her imaginary friend could talk to her, and she could explore an imaginary room instead of walking into the wall. Don't try to overexplain this, it will feel true so long as you're writing from your girl's point of view.....but if she is exploring a room that is a hallucination in its entirity then that will have to be imagination. might be easier to have one room in her house change, but leave it as a real room.
As an aside, most hallucinations in psychosis are auditory. Generally speaking, visual hallucinations are more common in organic illness eg brain tumours. People with psychosis do sometimes see things, but any doctor will want to do quite a through physical workup including MRI whenever visual halucinations are so prominent.
Does this count as a negative symptom: the girl has few friends and rarely interacts with those outside of her family. It's not that she really wants to but can't achieve that because she's too nutty -- it's that she doesn't even care about it. When people taunt her she, instead of reacting, just becomes more subdued, approaching a state of catatonia. Often, when someone tries to hold a conversation with her, she reacts by repeating a single word over and over again, first loud then soft then inaudible. (For example, when a boy asks if he could work on the cardboard house she's making, she says the word "mine" over and over again, without an obvious semantic context;
Anything there that could be an inaccurate portrayal of schizophrenia?
This is good too.
You're describing a combination of negative symptoms and defence mechanisms. It's easy for someone with psychosis to feel overwhelmed. A possible negative symptom is thought disorder, and that can just slow people up a bit. Some people describe it as thinking through treacle. Figuring things out can just be hard and it can take all your energy to stay focused.
your girl might be easily overwhelmed by someone interfering and not know what to do so just try to protect herself by withdrawing. Her lifestyle might also change as she may be better able to focus alone in her room without a million distractions.....just like sometimes we write better by stopping people interupting us and taking oursleves off somewhere quiet. isolation is a normal behaviour for a lot of us when we're stressed, psychois means your girl is alrady dealing with more than she can understand and isolation is a very natural response.
Basically, if you don't try to make every single aspect of your girl's behaviour a symptom, and remember that like the rest or us she has defence mechanisms, an imagination, and that how she perceives things is coloured by her experiences then you're good. Someone with psychosis doesn't stop being human, they just suddenly have a lot of frightening things to deal with at a time when their memory, concentration and ability to think clearly is impaired. The entire expereince can be overwhelming and isolation is a good way to respond to that.
I'd be happy to answer anything more specific if i can help.......but you're definately on the right lines.
Craig