The passage is in third person because it refers to her as Cathy or "her"
Rule 1. A subject will come before a phrase beginning with of. This is a key rule for understanding subjects. The word of is the culprit in many, perhaps most, subject-verb mistakes.
A bouquet of yellow roses lends color and fragrance to the room.
Rule 2. Two singular subjects connected by or, either/or, or neither/nor require a singular verb.
My aunt or my uncle is arriving by train today.
When the boy speaks to John, it shows that the boy is a bully and is antagonizing violence.
