Solange White is also charged with endangering the welfare of a child and aggravated assault.
Police say officers responded to a 911 call at a home in the 100 block of W. 46th Street at 3:41 a.m. Thursday for a child who was not breathing.
"We received a 911 call from another family member that the child was unconscious inside the residence," said Sgt. Sean Fullerton, Public Information Officer with Exeter Township Police.
The girl was rushed to the hospital where she was pronounced dead.
According to the affidavit of probable cause, officers arrived at the home and found White at the front of the home. Officers said she was" upset and crying."
Inside, they found a person inside the home performing CPR on the child. Police say officers continued life-saving efforts until medics arrived.
While tending to the girl, officers noted "visible bruising and marks" on her neck which were "consistent with strangulation-type injuries," according to the affidavit.
A witness allegedly told police he was woken up by White, who was repeatedly telling him that he needed to get a gun.
Then, according to the affidavit, that witness said he asked White, "What have you done?"
That witness said he checked on the children inside the home and found the three-year-old girl not moving and blue in the face.
White remains in custody.
Police say the child's mother and father were home, along with their one-year-old baby.
"The family is wonderful," said neighbor Cathy Fry.
Fry lives next door and says she used to babysit the little girl. She tells Action News the mother was going through postpartum depression.
"She was seeing doctors and she was in a home for a while. I thought she seemed better. They were just over," said Fry.
Crime scene technicians were in and out of the home Thursday.