In the suit, which seeks more than $50,000 in damages, Kristina McManigell alleges Eriluis Vaz made advances toward her three times -- twice while she was naked -- when she was in the female jockeys' room at Parx in Bensalem on Dec. 7, the Philadelphia Inquirer reported.
McManigell, 23, feared rape and screamed for help, the suit said.
McManigell's attorney, Adam S. Barrist, said in a statement she had come to Philadelphia from the rural south as a young woman "seeking to break into the male-dominated sport of thoroughbred horse racing."
"Just as she was beginning to make significant headway in her career, this happens to her," the statement said.
Alan Pincus, the attorney for Vaz, 28, said he could not comment because he had not seen the suit.
Two years ago, Vaz got into a fight with another jockey during a race at Parx, then called Philadelphia Park, and was suspended for 200 days.
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