Prosecutors say Wilborn used "tremendous blunt force" on her daughter Millicent on December 17 while her husband was at work. At about 4 p.m., Wilborn called 911 to report one of her twins was not responding. The baby was taken to the hospital, but later died of a ruptured heart. Further examination of the toddler showed she had fresh and old fractures to her ribs.
Authorities say the other twin had a fractured skull. Wilborn is accused of physically abusing the twins between Oct. 17, 2009 and Dec. 17, 2009.
The other two children did not exhibit any physical signs of trauma.
Wilborn is charged with one felony count of assault on a child with force likely to produce great bodily injury resulting in death and three felony counts of child abuse. If convicted, she faces a maximum sentence of 25 years to life in state prison.
Wilborn is being held on $1 million bail.