Nina Holiday is a young analyst who became part of the team after the death of Barry Frost.
Her first appearance in Lost & Found has her impressing Frankie when she didn't need to get up to speed on the case. She continues to impress her colleagues in all of her appearances.
In Bridge to Tomorrow, she mentions to Maura that a 14 year old killed her boyfriend Marcus, who was a teacher, to get in a gang. She also mentions that she liked how someone now knew what happened.
In A Bad Seed Grows, Nina is taking a night class in astronomy. She tells Frankie that they had a class discussion about UFOs, and Frankie blurts out that he saw a UFO once. He's embarrassed by the admission, but near the end of the episode, Nina gifts him with a telescope and keys to the building's rooftop. Frankie says he used the telescope all the time with an app.
In 5:26, Nina reveals to Jane that she was given a bible by her parents when she joined the force.
It is revealed in Two Shots: Move Forward that she had gotten shot in A Shot in the Dark. Immediately afterward, Frankie Rizzoli rushed over to her despite having a date to the wedding. When she awoke in the hospital, he was the first person she saw. Later that same episode, he is the one to pick her up as she is leaving the hospital.
In Dangerous Curve Ahead Frankie kisses Nina, who rushes off due to him being the first person to kiss her since Marcus. Later in the episode, they begin to date after she reveals this fact to Frankie. They hide the relationship until Shadow of Doubt.
In 2M7258-100, she second guesses herself in the field when chasing a suspect with Frankie.
In 65 Hours, she gets Frankie Bruins tickets.
In Stiffed, Frankie proposes on the roof of the BPD as they stargaze. She accepts immediately but they don't reveal the engagement right away due not having a ring. In Yesterday, Today, Tomorrow, he asks for old earrings from his mother that he uses to turn into an engagement ring. She creates an algorithm to enter her into contests so to be able to go anywhere on their honeymoon, causing her to win one of the sweepstakes. As they went to announce their news, Korsak revealed that he put in for retirement, so they postpone revealing their engagement. She ends the series as Frankie's fiancee.
- In Burden of Proof, her cell phone case is revealed to have "bling" on it. In that same episode, she mentions knowing how to make meringue.
- In Foot Loose, she mentions not liking lakes.
- In Family Matters, she shows knowledge of where to hide a handcuff key from bondage during sex.
- In Dangerous Curve Ahead, she admits that she likes French fries with Thousand Island dressing.
- Despite the free desk from Barry's passing, she is usually seen sitting behind a computer.
- After Korsak gives her some advice, she starts going out into the field.
- She was good friends with Susie prior to her death as seen in Imitation Game.
- She has a wedding hat as seen in A Shot in the Dark.
- In 65 Hours, it is mentioned that she likes magic tricks, which Frankie learns for her. She tells Angela that Frankie has been teaching her how to cook Italian food, including Chicken Parmesan. She also mentions that she likes Opera.