Mackenzie Shirilla didn’t act like somebody facing a lengthy sentence when she first came to prison, a former fellow inmate claims.

While speaking exclusively to PEOPLE, Kat Crowder, who spent six months in prison with Shirilla, insisted she “was very happy-go-lucky” whenever she saw her on the grounds.

Crowder said, when questioned whether Shirilla appeared to regret her actions, “From my observations of her in prison, she never had any behaviors that mirrored that of someone who was remorseful.”

“Full face of makeup, bright accessories and laughing constantly. Of course I don’t know what was going on in her mind but from the way she acted and carried herself, remorseful was the last thing she gave off,” the content creator — who shared a glimpse into her time behind bars at the Ohio Reformatory for Women alongside Shirilla on TikTok — continued.

Renewed interest in Shirilla’s case follows the release of the Netflix documentary The Crash, which examines the July 2022 car crash that killed her boyfriend, Dominic Russo, 20, and friend Davion Flanagan, 19, while she was behind the wheel.

Shirilla, now 21 and currently still housed at the Ohio Reformatory for Women in Marysville, is serving two concurrent sentences of 15 years to life in prison after being convicted of murder, vehicular homicide and other charges.

Prosecutors argued during her 2023 bench trial that she intentionally crashed her sedan into a brick wall in Strongsville, Ohio, at nearly 100 mph after her relationship with Russo had become strained. Although she was 17 at the time, she was tried as an adult.

Meanwhile, Crowder was sent to prison in April 2024, and she has been open about her time behind bars on TikTok, where she has over 147,000 followers.

She said of what surprised her the most about Shirilla’s personality was her “nonchalant demeanor.”

“If I was serving 15 years [to] life in prison I would simply be devastated,” Crowder said. “I wouldn’t be able to get myself up to put makeup every day and do my hair, let alone have girlfriends. I think that’s what was the most shocking to me. She didn’t even portray herself as someone who’s quite possibly serving the rest of her life in prison.”

Crowder told PEOPLE that “the documentary version” of Shirilla was someone she had “never seen.”

“From the way she sat down at that table, the way she spoke and the way she looked,” Crowder said, adding that the two “were never friends in prison but I saw her for hours at a time each day. She was very girly and light and [in] the documentary [she] came off as very dark and smug.”

The judge in Shirilla’s case previously described her in court as “literal hell on wheels.” However, she and her family have always maintained that she suffered a medical episode and that the crash was an accident.

Shirilla will become eligible for parole in 2037.

The Crash, which features interviews with both Shirilla’s family and the victims’ loved ones, was released on Netflix on May 15.