The Springfield Township Police Department said Thursday the woman has been taken into custody and arraigned.
They are still searching for the male suspect who police said threw the baby. Police said they do know his identity.
It happened at the Target store on the 1200 block of Baltimore Pike.
Police said the man and woman were shoplifting baby formula while carrying a baby strapped in a car seat.
While trying to get away from store security, police said the man threw the baby and car seat at security staff.
Investigators released images of the man and woman who allegedly attempted to walk out of the Target store with a shopping cart and backpack filled with formula.
When approached by store security, the woman took off. The man allegedly threw a car seat with a child inside of it at the security employee in the process.
"He threw the baby at him, the car seat tipped, the baby fell over, out of the car seat and rolled out," said Police Chief Joe Daly.
It was not clear if the child, who is estimated to be under one year old, was hurt in the fall.
Police said the security guard picked the child up and handed him back to the woman who claimed to be the child's mother.
The couple got away before officers arrived at the store.
Police said they have identified the male suspect.