Aretha Wilson entered the plea as part of a plea deal Friday in Los Angeles County Superior Court. She is expected to be sentenced to two years in prison on Nov. 22.
The Academy Award-nominated actor required surgery to repair a gash on his face and neck from the 2005 attack.
Wilson went to Canada after the attack and returned to Los Angeles to face the charge earlier this year. The 40-year-old had pleaded not guilty and was slated to begin trial on Friday.
She faced up to seven years in state prison if convicted.