Daisy Coleman, an advocate for sexual assault victims who became the subject of a Netflix documentary after saying she was raped at age 14 in Missouri, died by suicide in early August, according to her mother and a co-worker. She was 23.

Her mother, Melinda Coleman, announced the death Aug. 4 on Facebook.

“She was my best friend and amazing daughter,” Coleman wrote. “I think she had to make it seem like I could live without her. I can’t. I wish I could have taken the pain from her! She never recovered from what those boys did to her and it’s just not fair. My baby girl is gone.”

Daisy Coleman was found dead in Denver after her mother called police to check on her, said Shael Norris, executive director of SafeBAE, a group Ms. Coleman co-founded to help young victims of sexual assault. Norris said she heard the news from Ms. Coleman’s brother.

Ms. Coleman appeared in “Audrie & Daisy,” a 2016 Netflix documentary that followed her and her family as they dealt with her assault and the hostile reaction of the community in Maryville, Mo., to her allegations. She acknowledged in online comments that she had tried to kill herself at least twice before.

The other girl featured in the documentary, Audrie Pott, 15, died by suicide days after she said three boys sexually assaulted her in September 2012 in Saratoga, Calif.

Ms. Coleman was the driving force behind the formation of SafeBAE after the documentary, said Norris, who called her death “an irreplaceable loss.”

Norris said that Ms. Coleman “was really, really good at what she did,” because teenagers who had been assaulted knew she understood their problems.

“It’s a huge loss for the culture in general because I think it was her resilience that has inspired so many other survivors to get help and speak out,” Norris said.

On Jan. 8, 2012, the then-14-year-old Ms. Coleman and a 13-year-old friend sneaked out of the Coleman house and were picked up by Matthew Barnett, who was 17 at the time, and some other boys. They took the girls to a party at Barnett’s house.

Ms. Coleman told investigators that she was given a clear liquid before being raped in a bedroom while a second boy recorded the assault on his cellphone. Officials said during the investigation that the video no longer existed. The boys then left her on her porch, where she stayed in freezing temperatures for several hours before she was found.

Barnett admitted to having sex with Ms. Coleman but said it was consensual.

Ms. Coleman’s case was taken up by advocates for sexual assault victims nationwide and prompted rallies and outrage, particularly after a Kansas City Star report about the residents of Maryville reacting negatively to the Colemans.

Barnett pleaded guilty in January 2014 to a misdemeanor child endangerment charge and was sentenced to two years of probation and a four-month suspended jail term.

His sentence came after Robert Rice, Nodaway County’s prosecutor at the time, and Jackson County Prosecutor Jean Peters Baker determined that there was not enough evidence to pursue a rape charge. Baker was brought in to reopen the case after the Colemans and others criticized Rice for dismissing a felony charge against Barnett.

Melinda Coleman alleged that Rice dropped the felony charge because of political pressure — Barnett’s grandfather was a four-term Missouri state representative who was a state trooper for 32 years. Rice said he dropped the charge because the Colemans stopped cooperating with his investigation.

— Associated Press