TMZ Sports obtained her 911 call in which she identified Foster and said, "He took my phone and broke it and slapped me in my face."
The 49ers announced they released Foster on Sunday. ESPN.com reported he was arrested on a charge of domestic violence prior to Sunday's game against the Tampa Bay Buccaneers. The woman in the call said the incident occurred at the team hotel in Tampa, Florida.
Evan Sernoffsky, Eric Branch and Steve Rubenstein of the San Francisco Chronicle reported Foster posted $2,000 bail and was released from jail on Sunday.
The report identified the woman as Elissa Ennis and cited a source close to her family who said she was diagnosed with a concussion at the hospital. It also cited police who said, "Foster slapped her phone out of her hand, pushed her in the chest area, and slapped her with an open hand on the left side of her face. ... Officers observed a 1-inch scratch on the victim's left collarbone."
Both the San Francisco Chronicle and ESPN detailed Foster's previous legal incidents prior to Saturday's arrest.
He was charged with a second-degree marijuana possession in January, but the charge was dismissed following a diversion course. He was also charged with domestic violence, criminal threats and weapon possessions felonies in April stemming from a February altercation at his California home.
The domestic violence and criminal threats charges were dropped, while the weapons charge was reduced to a misdemeanor. Foster was sentenced to two years of probation, 232 hours of community service and a $235 fine.
The NFL suspended Foster for the first two games of the 2018 season following the marijuana and gun charges.
According to the San Francisco Chronicle, police were also called to Foster's California apartment in October because of a domestic disturbance involving Ennis. While there were no signs of physical injury, police were called after reports of a loud argument.