The Polk County Sheriff's Office said Friday that 30-year-old Vivian Vosburg has been booked into the county jail on two counts of child abuse with bodily harm and four counts of child neglect.
Officials say Vosburg beat a child with her fists in her home as several other children watched.
Sheriff Grady Judd said at a news conference that one child in the home took a cellphone video of the beating and posted it on Facebook.
Judd says Vosburg is the stepmother of one of two girls charged with felony aggravated stalking earlier in the week. Officials say the girls bullied and harassed 12-year-old Rebecca Sedwick before she committed suicide.
Accused cyberbully's boyfriend voices regret
Friday morning, the boy at the center of the case came forward. John Borgen, 13, is currently dating the 14-year-old girl accused of cyber-bullying 12-year-old Rebecca Sedwick.
Police say the teen told Rebecca she should, "Drink bleach and die," and should "kill herself," because she was "ugly."
Police say the attacks erupted out of jealousy over Borgen's attention. Borgen says he doesn't think his girlfriend is responsible for a Facebook post saying she didn't care Rebecca was dead.
Reporter: Did you know about that?
Borgen: Yeah. I thought somebody hacked her account.
Reporter: How often do you think about Rebecca?
Borgen: I think about her almost every day, knowing that she got bullied. I could've stopped it.
This 14-year-old girlfriend is now in jail. She and another 12-year-old are charged with felony aggravated stalking.
ABC7 News contributed to this report.