Nicole Bradburn pleaded not guilty to seven counts of unlawful sex with a minor, 11 counts of committing a lewd act on a child, and nine counts or participating in oral copulation with a minor, according to court records.
The alleged crimes, which are all felonies, occurred between Oct. 1 and Feb. 14.
Antioch police said they started investigating the case in January after the victim's parents became suspicious about the amount of time their son was spending with Bradburn.
The boy, however, refused to admit to the relationship because Bradburn had allegedly convinced him she was in love with him, police said.
It wasn't until the boy's father discovered what police characterized as an "incriminating text message" from Bradburn on his son's cell phone that the boy finally admitted that he had been having a sexual relationship with Bradburn, police said.
Detectives served a search warrant on Bradburn's house last week and arrested her.
She remained in custody today at the West County Detention Facility in Richmond in lieu of nearly $1.7 million bail.
She is scheduled to return to court April 5 for a preliminary hearing.
Antioch police have said they believe there could be other victims and are asking anyone with information about the case to call Detective Danielle Joannides at (925) 779-6931.