She says Kelly initiated "non-permissive, painful and abusive sex" and failed to inform her he had the incurable virus herpes, which she says she then contracted.
In the letter, a person identifying himself as R. Kelly writes that if the suit went forward, he would have "10 personal male witnesses" testify about Rodgers' sex life.
Rogders originally filed a complaint with the Dallas Police Department in April 2018, claiming that Kelly mentally, physically, and sexually abused her during an eight-month relationship that began in 2017 when she was 19 years old.
The Chicago Sun-Times' first investigative story about allegations of Kelly as a sexual predator was published in 2000, and one of the reporters, Jim DeRogatis, continued to follow the story over the decades at a number of publications.
In a prepared statement at the press conference, Rodgers, speaking very quietly, said, "Taking a stand against R. Kelly, someone who has been termed "the King of R&B" and is loved by many, has not been easy".
Steve Greenberg, an attorney for Kelly, said in an interview on Friday that there was no evidence to support the accusations contained in the documentary, calling it a "for-profit hit piece full of falsities, full of mistakes".
Appearing on Good Morning America last week and discussing R Kelly's rumoured marriage to Aaliyah when she was 15, his lawyer Steven Greenberg said, "My understanding is that she did not claim to be 15 and, in order to get married, she had to lie about her age".
Kelly's camp has in the past denied that he knew the late pop star was just 15 when they Wednesday in secret in 1994. In a 1994 documentary about the singer who had just dropped his debut solo album 12 Play, after leaving his original group Public Announcement, R. Kelly reveals that he's producing a singer by the name of Aaliyah, who in his own words "is 14 and real street".
The letter writer added later that, "I am exempt and not subject to this court so I don't know why you are even addressing me".