My sister schizophrenic as per dr.,sometime she behave normal sometime not she believes things about the past that are not true suggest us !!

Surviving Schizo-: phrenia is a book by E. Fuller Torrey. It is written for the family members of a person w/schizophrenia. Please always keep in mind that your sister's disorder causes her erratic behavior. Be clear and consistent can be helpful. Peace and good health.

Fixed delusions: If your sister is convinced about unreal events or actions of other people - these may be fixed delusions. It is harder to treat them, compared to other symptoms of schizophrenia. Combining medications with family therapy might help.