In an open letter addressed to club president Joan Laporta, Giovana Queiroz said she suffered "abusive behaviour" at the hands of a club director during her time at the club.
Giovana, 18, added that an individual at the club "wanted to destroy my reputation, undermine my self-esteem, and degrade my working conditions."
The forward, who is now on loan at Levante, said the problems started after she accepted a call-up to play for the Brazilian national team.
"I received indications that playing for Brazil would not be good for my future with the club," she wrote. "They were cornering me in an abusive way so that I did not play for the national team.
"In February 2021, I was illegally confined by the club. They claimed I had been a close contact of a COVID case. After completing my quarantine, I received permission from FIFA to join the Brazil squad in the United States.
"When I returned to the club, a meeting was held with a club director in which I was unfairly accused of breaching protocol and travelling without club authorisation.
"From that moment on my life changed forever. I was exposed to humiliating situations for months within the club. It was clear that he wanted to destroy my reputation, undermine my self-esteem, and degrade my working conditions."
Giovana, who joined Barca from Madrid CFF in 2020, said the club was not directly responsible for the abuse but should be "responsible for ensuring mental and moral integrity over any type of abuse."
She added: "The memories, the trauma and the after-effects are likely to last for years. My personal and professional life was deeply affected."
A Barca spokesman told ESPN: "The allegations of moral abuse, workplace harassment and psychological violence are not true.
"Giovana was a close contact of a positive COVID case and the club told her she couldn't travel to Orlando in the United States with the Brazilian national team due to Spanish government regulations.
"She complained to the club's compliance department and to FIFA. Barcelona's compliance department and FIFA found that they had both acted properly. The case was closed."
ESPN have reached out to FIFA for comment, but the governing body has not yet responded.