Police said 26-year-old Sarah Brady acted in self-defense in killing Katherine Smith on Thursday. No charges were filed.
Smith, 22, had been falsely telling neighbors for weeks that she was pregnant, and a search of her apartment after her death revealed a full baby nursery, investigators said.
"She had everything in place that you'd expect to have in place with a newborn coming," said Steve Hensley, police chief in this Cincinnati suburb.
Brady, 26, was treated for cuts at a hospital.
Police said that about a week ago, Smith called Brady, a stranger, and asked her to come over and pick up a mistakenly delivered package. Brady picked up the package, the two spoke briefly and she left, according to police. Thursday's attack occurred after Brady went to pick up a second package at Smith's apartment, police said.
In December, a Missouri woman was strangled and her baby was . The baby was later found alive, and a Kansas woman was charged with kidnapping resulting in death.