Ashwani Kumar alias Annu alias Anuwa (28) and the 16-year-old girl were arrested by Ambedkar Nagar police.
A country-made pistol, which is said to be the weapon used in the crime, along with a live cartridge were seized from Kumar's possession, according to police.
"Kumar has been involved in several criminal cases. He used to indulge in pick-pocketing with his associates and lived an extravagant life from the money earned through it," said a senior police official.
In an altercation on Tuesday evening, Neelofar slapped the second girl.
More From This Section
Apparently upset over the issue, the girl asked Kumar to teach Neelofar a lesson, police said.
At around 8:45 pm on Tuesday, Ashwini along with an associate barged into Neelofar's house and shot her in the neck before fleeing on a bike.
She was first taken to AIIMS Trauma Centre and then referred to Max Hospital, where she is still battling for her life.