Fourteen-year-old Roxalie Villafuerte sustained a gunshot wound in the head and was pronounced dead on arrival at the Medical City of Parañaque.
Suspect Jenalyn Malintal, 20, tried to escape but was immediately apprehended by policemen.
Investigation showed the incident happened at around 10:30 p.m. at the familys house in Creekside, San Antonio Valley, Barangay San Antonio.
Inspector Glen Tigson, Station Investigation Division (SID) chief, said the victims father, Valentino, got upset with Malintal for meddling with his daughters life. Malintal had Roxalie employed as a spotter at a billiard hall.
At their living room, the couple got into a heated argument and Roxalie tried to pacify them.
But Malintal grabbed an unlicensed caliber .38 pistol and shot the teenager.
According to Tigson, the suspect claimed that she merely threatened Valentino with a gun. It accidentally went off and hit Roxalie.
However, the victims nine-year-old brother told investigators a different story.
The boy said he saw Malintal grab Roxalie and pointed the gun on her head, threatening Valentino that she would shoot his daughter.
"We have to determine the veracity of the boys statement. If that was what really happened, then we would charge the suspect with murder," Tigson said.
Malintal, who is jobless, claimed to have thrown away the gun after the incident.
Tigson said Valentinos first wife died exactly a year ago. Valentino, who is in his late 40s and a contract worker at a memorial park, has been living with the suspect for the past four years.
Malintal is now detained at the Parañaque police detention cell. Nikko Dizon