When subject of the sentence performs the actions, then the sentence is in active voice. When the subject of the sentence is the receiver of the action, then the sentence is in passive voice
In the above sentence:
Maddy does not perform any action, i.e. Maddy IS NOT PERFORMING THE ACTION OF WRITING. Rather, Maddy IS ACTED UPON AS ONE OF THE BEST WRITERS; hence, Maddy is the receiver of the action. Hence the sentence is in passive voice.
