The best description of her delusion it is a positive symptom.
Option c
Explanation:
Schizophrenia is a severe mental disorder in which the line between real and imaginary does not exist for the patient. It has positive and negative symptoms. The positive symptoms are the ones which are noticeably present. They are psychotic symptoms evident by the behavior of the patient.
One of these symptoms is delusion. The patient tends to believe an unrealistic facts such as being followed by some secret government agents or being a part of one. They might believe that they are some prominent/famous personalities such as an actor/person of historic significance or any other individual known to majority of population. Like in Andrea’s case, she is delusional and believes she is the Virgin Mary.