The Buffy the Vampire Slayer star, 37, alleges O'Brien attacked her in front of the latter's children with Eisler in Kingston, Ontario.
Swanson says, "I had to go the police station where I had an appointment at 9 p.m. to begin the process of being arrested."
Swanson, who has been released on CAN$500 ($468) bail, claims police took photographs of her injuries, which she alleges were given to her by O'Brien.
The actress plans to press for criminal charges against O'Brien.
Professional ice skater Eisler and Swanson caused a scandal when they started dating while co-starring in TV talent show Skating with Celebrities in late 2005--while Eisler was still married to O'Brien, who was then pregnant with the couple's second child, Seth Keenan.
Eisler divorced O'Brien in January--a month before Swanson gave birth to their son Magnus Hart.
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