Phelps described Mariah as a "loose cannon," while Grimes has characterized her as a "bad girl with a heart" and more dimensional than what viewers would expect her to be.

Mariah's relationship with another woman proved controversial due to the soap opera's conservative audience, with TV Insider reporting that a gag order prevented Grimes from discussing it with the press.

[1] Grimes had previously portrayed the role of Cassie Newman, Mariah's twin sister, on the series from 1997 to 2005, when the character was killed off in a car accident.

[2] Grimes was seven when she originated the role of Cassie and, in 2000, became the youngest recipient of the Daytime Emmy Award for Outstanding Younger Actress in a Drama Series.

[6] When Grimes learned that she was no longer portraying Cassie's ghost but another character, the actress stated: "I heard rumors that the storyline might be changing, that somehow I would be continuing on the show.

I had all these ideas going through my head but I was thinking of the obvious things, like maybe Cassie had a twin sister nobody knew about (...) But what the writers came up with is so much fun and so unexpected," stating that the new character had "potential to go all over the place".

[2] In a featured interview with Soaps in Depth, Grimes stated: "Looking back after a year, it's kind of crazy to see how things have developed.

[11] Executive producer Jill Farren Phelps labelled Mariah as a "have-not", which is a "very powerful" driving force for her behavior.

[8] Victor's intentions were to make his son, Nicholas Newman (Joshua Morrow) believe Sharon is mentally unstable and "seeing ghosts" so that he would not become romantically involved with her again.

[5] Co-head writer Jean Passanante noted that the character's edge became clear in her interactions with Victor, finding it "startling and exciting".

[6] Executive producer Jill Farren Phelps stated that it was the soap's intention to make Cassie's doppelgänger turn out to be Mariah all along.

Helen Copeland (Karina Logue), a "bitter" woman who claimed to be Mariah's mother for her entire life,[23] was the nurse present who bought the baby for Ian from Dr. Hill, who needed the money for gambling debts.

"[26] After the revelation of learning Sharon was her mother, Mariah grows closer to Kevin Fisher (Greg Rikaart) who is also going through a rough patch.

Grimes noted that Mariah is "figuring out where she stands in this new city, with this new family, having had the rug pulled out from under her about what she thought she knew about her past", describing her as being in a phase of "soul searching".

[30] A same-sex relationship between Mariah and a new character named Tessa was one of the stories then-head writer and executive producer Sally Sussman Morina had pitched to CBS after being hired in September 2016.

"[31] Mariah and Tessa's kiss marked the first time The Young and the Restless had delved into a relationship between two major characters of the same gender.

Grimes believed that it was always the writers' intention to revisit the couple, observing: "So much happened between Noah, Mariah, and Tessa that you couldn’t just jump into a relationship after all of that went down and she stole the notebook.

"[35] Due to same-sex relationships being "uncharted territory" on The Young and the Restless, Grimes also felt that this slow pacing was necessary; "you gotta take your time and do it right," she said.

Nick, who is now involved with Sharon again, hires Mariah at his nightclub, The Underground, where she works alongside their son Noah Newman (Robert Adamson).

Mariah develops friendships with Kevin Fisher (Greg Rikaart) and Summer's husband Austin Travers (Matthew Atkinson).

"Through all these emotional scenes it was Camryn Grimes who made the story plausible with her top-notch acting as she went from hurt, to angry, to betrayal, to disbelief, to completely lost, while the whole time keeping the character's harder edges.

"[16] In the "Best and Worst of 2014" issue of Soaps in Depth, the magazine wrote of Grimes' return: "Sure, Mariah's storyline hasn't always made a ton of sense — Tyler's stalker sure chased him for a long time to give up on him so fast!

[29] Having been away from the daytime genre for a decade (a period in which other soap operas had featured LGBT characters), Sally Sussman Morina was "taken aback" by the negativity surrounding the kiss.

[31] However, it also received positive feedback on social media; Grimes responded to these reactions by writing: "Your strength is power, progress, and potential.

[28] Michael Logan of TV Insider reported that network executives were "super skittish" about the storyline, and that there was a gag order banning Grimes and her co-stars from discussing it with the press.

[30] Jeremy Helligar of HuffPost praised the show's depiction of Mariah and Tessa's feelings for one another as "just two women falling for each other and attempting to make sense of it without putting a label on it.

"[32] Helligar remarked that "gender almost seems to be an afterthought" in the storyline, "It’s backing up an assertion some of us have been making forever: Two men or two women fall in love the same way a man and a woman do.

[32] In 2021, Lynette Rice of Entertainment Weekly—who observed Mariah and Tessa to be the only "full-time, same-sex couple in daytime right now"—highlighted viewers' appreciation of "how organically the relationship developed.

The storyline earned Grimes her second Daytime Emmy Award, winning for Outstanding Supporting Actress in a Drama Series in April 2018.

[41] In August 2018, Grimes elaborated on receiving online backlash as a result of Mariah and Tessa's relationship, stating: "I’ve gotten over clapping back to everything because I realize it’s just not the important conversation.