Dawn Noel's complaint claims the 32-year-old singer arrived "in a disheveled and confused state" to the video shoot in Woodland Hills, Calif., on Aug. 19, 2013, and that "although the choreography involving Britney Spears was fairly basic, she was having difficulty learning the moves, performing dance steps and following simple directions."
The complaint goes on to say that after 30 minutes of rehearsal, Spears "twirled in an unbalanced and reckless manner, arms extended out to her sides and forcefully backhanded" Noel in the face, breaking her nose.
The singer's reps reportedly told the dancer that all of her medical bills would be paid, but later changed their minds and refused to cover her medical expenses.
Noel, who is looking for the case to go to trial, is suing Spears for battery and negligence. The dancer's lawsuit claims she suffered physical and emotional damages -- including disfigurement to her nose and emotional distress and anxiety -- after the incident.
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