Lane acknowledged that she'd signed a contract that would not guarantee her on-screen credits.
"I didn't really specify anything in my contract about getting onscreen credit or anything," said Lane. "I didn't do the movie to get fame or recognition or anything."
Lane said her feelings about being credited changed late last year after Portman received an Oscar nomination for best actress and the movie's backers began an aggressive campaign on the actress's behalf.
"There's so much emotionally that goes into motivating yourself and being able to physically push yourself to reach a certain level, that you have to reach to be a professional ballerina with one of the biggest ballet companies in the world and to sustain that standard over a whole career," Lane said. "It really hurts for someone to say that, they got a personal trainer and they became what I spent blood, sweat and tears doing every day, all my life, in just a year and a half."
"A lot of the campaign was focused on the physical preparation, the transformation," Cagle said. "The Academy loves it when an actor does something besides act in a movie. There was in a lot of the marketing materials for "Black Swan," certainly the implication that Natalie became a great world class ballet dancer."
Lane acknowledged that while Portman trained hard for the film, her dancing technique was nowhere near as good as hers.
"I've been doing this for 22 years, and to say that someone trained for a year and a half and did what I did is degrading not only to me but to the entire ballet world," Lane said.
Wendy Perron, editor-in-chief of Dance Magazine, a choreographer and a dancer, said she knew of Lane's role in "Black Swan" and wondered why a soloist ballerina whose technical skills were vital to the complicated dance sequences was being cast out of the limelight.
"She's an artist," Perron said. "It's not just that it was difficult. It's that she brought an artistry to it, and Natalie Portman is a dramatic artist, a film artist. But Sarah Lane is a dance artist, and she helped make the movie what it was. ... It bothered me. I think she should get credit for it."
Perron wrote her opinion in a blog that was soon picked up in the national media, and "Black Swan" filmmakers moved swiftly to defend their star.
Portman has continued to decline to comment on the controversy, and told E! News last week, "I had a chance to make something beautiful with this film, and I don't want to give in to the gossip."
For Lane, the silver lining in this controversy may just be that ballet is taking center stage in a national discussion. An unanticipated opportunity to share the commitment and dedication of all ballet dancers.
"I have so much respect for this art form and the people who are able to do it so beautifully and I want to stand up for that," she said. "I want people to know how hard we work as professional dancers. What is not necessarily, really portrayed in the movie, is the beauty that ballet can create. How it can reach across oceans, and how it can bond countries who are completely at war."
Watch the exclusive interview on "20/20" TONIGHT at 10 p.m. ET