Kylie Hamilton, 27, was arrested Friday and is facing negligent child abuse resulting in serious bodily injury after police said she "willfully allowed" her boyfriend, 27-year-old Ronald Frazier, to severely beat her child.
The investigation began February 8 when Hamilton brought her child to WakeMed Cary with severe injuries including a fractured skull.
Police said they believe Hamilton knew about the incident and delayed getting medical help.
The hospital staff alerted the Cary Police Department to the injuries, per protocol.
As a result, Frazier was charged with attempted first-degree murder and felony child abuse.
Frazier was later arrested for assault on a female and felony strangulation, stemming from a separate, but possibly related incident, according to police.
He is being held at the Wake County Public Safety Center.