Schuman said she was 18 and Carter was 22 at the time of the alleged assault.
The singer said she did not talk about the assault earlier because her manager told her that Carter had the "most powerful litigator in the country".
Now, 15 years later, she decided to come forward after trolls targeted a female fan who claimed Carter had forced her to perform oral sex on him in 2006.
"Victim shaming is a core reason why victims don't speak out," she added.
"I can't help but feel empathy for her as well as sicken(ed) by the lack of belief and support."
Carter, who is married to Lauren Kitt and has a young son, is yet to publicly respond to her allegations. (ANI)