Cleo and Melody Carver develop a feud that starts with Melody bumping into Cleo in the cafeteria, and hits its peak when Cleo kisses Jackson to spite Melody, to which Melody responds by asking Deuce to the Monster Mash. Somewhere in the beginning of the book, Deuce explains that there was no romance involved at the dance, and gives Cleo a snake, Hissette, which was his mom's first gray hair. He entwines the snake around her wrist and turns it to stone, creating a bracelet. Cleo ends up being one of the few monsters totally against human-monster equality. She especially turns against the crusade when she's offered a photoshoot for Teen Vogue, which she gets her friends involved with as well, and it ends up on the same day as Brett's video shoot for the Ghoul Next Door, a film designed to show the RAD's true nature. She forms a shaky alliance with Bekka, and then backstabs her once she believes the video is deleted. She goes to her photoshoot, which somehow ends up with her, Melody, and Candace, and then learns that the film was sabotaged and uncensored, then aired. She ends up taking the blame by most of her friends. Cleo clears her name at an R.I.P., and ends up being one of the few families to stay in town. She and Melody find a common hatred in Bekka and become friends, and together set up and plan Clawdeen's Sassy Sixteen party, which ends up a huge success when she flaunts her RAD status along with everyone else. When a competition arises for a couple to be named sponsor of a nationwide contest that will donate a million dollars to a school, her and Deuce enter and find fierce competition in Frankie and Brett. Cleo rears her ruthless once more and would have won, had not Billy Phaiden switched the ballots. In the end, her and Frankie make up and salvaged their relationship.
Having gone shopping shortly before Ghoulish Literature, Cleo brings her purchases to class. This draws the attention of Venus, who does not approve of taking bags from the stores and unnecessarily burdening the planet. She tries to convince Cleo to take a reusable shopping bag with her from now, but only manages to irritate the mummy. The situation quickly escalates, both sides unwilling to budge, and Venus loses control. She hits Cleo with a pollen cloud, mind-controlling her into getting herself one solid shopping bag to use. Unable to resist, Cleo enthusiastically agrees, but her anger from before remains. A few days later, like almost everyone else at Monster High, Cleo has come under Sylphia Flapper's mind control and is not freed until a few days later by the efforts of Venus, Rochelle, Robecca, and Cy.
Monster High Diaries
Positively startling news reaches the De Nile household: Dedyet de Nile, wife of Ramses de Nile and mother of Cleo and Nefera has suddenly reappeared. Elated, Cleo shares the news with Frankie, Draculaura and Deuce, regaling them with tales of how fantastic she was, and announces that her family will be throwing a huge party in a few days to welcome her mother. Draculaura wonders if Cleo's mother might be different from how she remembers her, but Cleo is certain she'll be just as she last saw her. During the conversation, Frankie accidentally rips her skirt, and Cleo offers to help her repair it. The next day, Dedyet de Nile meets the family at long last, but everyone, Cleo especially, is surprised to see her wearing a worn shirt and jeans, and no make-up. Even more surprising, she makes a snack for herself in the kitchen without waiting for a servant.
Dedyet explains that after the family escaped from their home in Egypt, she found herself in a hideout, waiting for word from her family. With nothing to do, she took to reading from a massive library, and developed an interest in archaeology, as well as becoming less accustomed to the lush lifestyle she had once lived. When she eventually made her way to the Boo World to find her family, she decided to spend some time assisting at an archaeological dig. Before they could finish though, they were trapped inside a tomb, and were only released recently.
Although impressed by her mother's tales, Cleo is worried that she and her mother no longer seem to have anything in common, as well as what her friends will think when they realize Dedyet is nothing like she had described. When her friends ask about her the next day, Cleo doesn't give out the full details of her mother's new look. After helping Draculaura with a new fearleading routine, Cleo hits on the idea of giving her mother a complete makeover at a spa, reminding her of how she used to be.
After school she meets Clawdeen, and asks if she could make a dress for her mother to wear for the party. Clawdeen explains she'd love to, but she's currently busy trying to design a dress for Clawdia, and can't find the fabric she needs. Upon seeing the design for the dress, Cleo remembers that she has a similar dress in her closet, and offers to give it to Clawdeen to modify into her design. The two head to Cleo's place, where Dedyet asks if she can meet Clawdeen. Cleo suggests that it would be a good idea to have a makeover so she can look her best before she meets her friends. Dedyet states that she truly is happy with the way she is now, and is disappointed that Cleo doesn't seem to understand. Cleo realizes that she genuinely is happy that her mother is happy, and apologizes for suggesting the makeover. The two spend the night watching movies together, and reminiscing over Dedyet's stories of her time as archaeologist.
Realising that her mother probably wouldn't like the extravagant party she had planned, Cleo decides she needs to tone it down, despite Nefera's protests. She asks her friends for some help arranging the new party, telling them the truth about her mother's current look. Every one agrees they're sure to like her when they meet her, and Deuce is happy that he'll finally meet a member of Cleo's family that will actually like him.
Some time later, and with some reluctant help from Nefera, the party is redesigned as a 'come as you are' party. Dedyet meets Cleo's friends, and Cleo asks if they're amazed by how different she and Dedyet are now. Her friends state that Cleo and Dedyet do have one thing in common – both of them are incredibly caring and willing to help others.
Hopes and Screams
Cleo has to decline writing for the Gory Gazette, but she promises to throw a premiere party in honor of the new issue. She informs Deuce they'll need to find matching ensembles, but she is cut short when his snakes start loudly hissing at her. Deuce and Cleo are send to Bloodgood's office for disrupting Mad Science, but Deuce remains unable to calm his snakes or explain their behavior. He quickly runs off and Cleo, worried she might have to compete with his hair over his affections, follows him. Cleo spots him talking with Frankie in the creepateria and assumes he is following his hair's wishes and replacing her with Frankie. Broken, she returns home and lets Ghoulia comfort her. Going through a book on snakes, Ghoulia finds a possible solution: Cleo has to learn to play the flute in order to charm the snakes. Cleo doesn't hestitate for a moment and signs up for a rush lesson. Once she's ready, she invites Deuce to the clawditorium, where he stumbles over himself to explain that he never would break up with her. The reason his snakes got hostile was because he was preparing an anniversary gift for her and they didn't want him near her for fear he'd spoil the surprise. He gives her the earrings he bought and, flustered, Cleo tells him about her flute lessons. Deuce tells her to play it for him anyway as her own gift, which she gladly does. Cleo and Deuce are awarded a Scream in the latest entry of Clawdeen's Gory Gazette vlog Fashion Screams and Yawns and later shares a tough practice ferleading practice session before the casketball game with her.
I Only Have Eye for You
Cleo goes shopping with Frankie and Ghoulia, she finds a very expensive dress. She's about to buy it but her wallet is short. Cleo goes to her father and demands an advance in her allowance. He is about to comply until Nefera informs their father that Cleo will spend their money on her dates with Deuce. Ramses then reminds Cleo he has never approved of Deuce and he would not pay for their dates. Cleo states that she loves Deuce and they'd be happy together regardless of Ramses' approval. Ramses then cuts her allowance completely.
Deuce later surprises Cleo with a dozen fluffily friends, which makes her happy. It puts a damper in her plans when he said he spent all his money on the fluffy friends, she is disappointed but not angry. Since neither have allowances for the weekend she declares they'll skip the dance. Deuce is fine with this plan and they spend the weekend hanging out at his house. Cleo plays video-games, and wins, and enjoys the dinner Deuce cooks for them. Deuce says he can always depend on Cleo to be resourceful. Cleo states that they will go to the dance, she'll wear an old dress.
Cleo and Deuce go to the dance and are the center of attention. Valentine appears to Draculaura and is threatened by Cleo to prove his innocent claims. He admits to bothering many of the couples before the dance that week. His interference with Cleo & Deuce was calling Cleo's father and offending him in Deuce's honor.