McKenzie has long, auburn hair tied up in a ponytail. She has fair skin and gray eyes. She wears a navy blue officer's uniform with her radio clipped to her chest.
Rebecca was first portrayed as a nervous rookie, but later became more assertive in her duties, seen when she cuffed Jamie Brooks for embezzlement. She also seems to be light-hearted, enjoying her time protecting Cassandra Leigh on the movie set as she humored herself with the prop guns.
Nevertheless, she is a dutiful servant of the law, as she struggled to stay awake and remember Tull's attack on Leigh despite being severely wounded by the ordeal.
Dave gave her a pep talk on how to deal with murder cases because it was her first time investigating a gruesome case, over time, they both seem to respect and like one another.
- The player gets a chance to play as her for diamonds.
- McKenzie is left fighting for her life when John Tull shoots her in Chapter 13. However, in Chapter 15, she pulls through and attends Sam and Dave's medal honours.
- She makes a cameo in The Freshman, Book 4 as a police officer that helps you out when Zack's van breaks down and you don't have a car repair kit. She writes you a ticket for the lack of seat belts.
- She appears seemingly recovered at the end of Most Wanted Book 1. However, it appears that she has resigned from the LAPD and now works in quieter towns with lower crime rates per her cameo in High School Story, Book 2, Chapter 13.
- It is revealed in Chapter 15 of Endless Summer, Book 2, that she is the sister of Jake, a main character in that book.
- Some fans believe her motivation for joining Law Enforcement is to see if her brother really did commit an act of treason and possibly prove his innocence.
- She makes a cameo appearance in Red Carpet Diaries, Book 2, Chapter 10.