How can you distinguish dementia from schizophrenia?

An old woman came to our pharmacy.
She brought lots of medicines.
They were all mixed up.
We had to check and re-sort them.
She said her daughter-in -law hides her medicines.
That's weird.

She had a prescription of Risperdal, a medicine for schizophrenia.
Does the delusion come from the disease?
She may have dementia.

Anyway we have to support her from now on.