“Hell on wheels” murderer Mackenzie Shirilla boasted about being given a twisted nickname in her all-women lockup, her prison ex-girlfriend claimed.

“We started talking and she told me her nickname was ‘Shirilla the killa,’ like, that’s what her bunkmates called her,” former Ohio Reformatory for Women inmate Shyann Topping told the US Sun.

Topping, 27, told the outlet she dated the 21-year-old convicted double murderer for a couple of weeks behind bars — where Shirilla was a very demanding girlfriend.

“If we did argue, it’s because I didn’t come outside on time,” the woman said, explaining that the duo would often get intimate in the prison yard.

“And she’s like, ‘I was waiting for you. Where were you? Like, if this is how it’s gonna go, I just won’t talk to you,’” Topping said.

The lesbian love affair was cut short when Topping was released from her prison sentence just two weeks after they met — devastating Shirilla, who she claimed professed her love.

“Mackenzie was upset that I was leaving. She would tell me all the time, ‘I wish we met sooner, before you were about to get out. I wish you would have talked before this,’” the former inmate said.

Topping also claimed Shirilla — who was convicted of intentionally crashing her car and killing her boyfriend and friend in 2022 — talked about what their relationship would look like outside prison, and shared many other grand plans for the future.

“She said she was just gonna live it [up] if she gets out,” Topping told the Sun.

“Like, she’s gonna go back to concerts. She’s gonna travel. She’s gonna be an influencer and write a book when she gets out about everything that happened.

“She said it might take some time, but she’s gonna get out and live it again,” the former inmate said.

In the meantime, Shirilla appeared “pretty and bubbly” behind bars, and sported a “popular girl aura,” according to Topping and a second former inmate, Mary Katherine Crowder.

“When I was in there with her, you’d look at her and she had her makeup done every day, she was very well put together — almost like preppy,” Crowder, who served about six months alongside Shirilla, previously told The Post.

“Everyone knew why she was there, and she walked around like she was this famous person within prison,” Crowder said. “She always had makeup done, hair done, her clothes were altered to fit her body tighter or be different.

“She definitely carried herself like she was the Regina George of prison … she was very much like an ‘It girl,’” she recalled — referencing the “Mean Girls” clique leader.

Both former inmates also said they never saw Shirilla — the subject of a new, No. 1 Netflix documentary, “The Crash” — show an ounce of remorse for her teen victims.

“It was always bubbly, smiley, happy, line-dancing every Friday. I’ve never seen her sad, honestly,” her alleged ex-girlfriend reportedly said.

“She just stays real busy all day,” Topping said, adding that Shirilla frequently did arts and crafts and jammed out to hip-hop music from Kid Cudi and Playboi Carti on her prison-issued tablet.

During their brief relationship — which kicked off because Topping “thought [Shirilla] was beautiful” compared to the rest of the lot — the former inmate believed the double murderer’s claims that the car crash that landed her in prison had been accidental.

“I thought, okay, if this girl really is innocent, it would be an amazing story to get out, write a book and blow up off of that and even honor your boyfriend and his friend,” she said.

“Then if she did blow up, okay, she could set the families off with her, what is it? Publishing money.”

However, since her release, Topping has come to believe the truckload of evidence that prosecutors had against her alleged ex-girlfriend — and is no longer buying that Shirilla suffered from health issues.

“Now I’m thinking, okay, she was just trying to grab a piece of fame. I don’t think she would do any of that for the families if she got out,” Topping said.

“I think she would throw up a big middle finger to them like, I got away with it.”

Shirilla, who was 17 at the time of the crash, was ordered to serve two concurrent sentences of 15 years to life following a dramatic bench trial in 2023. She is appealing her conviction for a second time.

“It’s not gonna work. You have to show remorse. You at least gotta tell the families what happened,” Topping said about her appeal efforts, and slammed Shirilla’s crimes as “sick” and “evil.”