The footage that emerged on Monday evening purportedly shows Asma Rani in hospital shortly before her death, naming one Mujahid Afridi as her killer.
Rani, a third-year medical student, was shot on Saturday afternoon in Kohat, and died in hospital on Sunday.
Her family alleges that Afridi killed Rani after she refused to marry him, having also made previous threats against her.
The country's Supreme Court also took suo motu notice of the murder on Tuesday.
Chief Justice Mian Saqib Nisar ordered that a report on the case be submitted in the court by Wednesday.
"We heard tales that the Khyber Pakhtunkhwa Police has become a lot better; what is the force doing after this girl was murdered in Kohat?" the Chief Justice asked, adding that there seems to be no mechanism set for the investigation.
When first reporting the attack, Rani's brother Muhammad Irfan named two brothers - Afridi and Sadiq Ullah - as the attackers.
Ullah was arrested in Kohat on Tuesday but his brother was yet to be found. Afridi is believed to have fled to Saudi Arabia. A red notice has been issued by Interpol for his arrest, Pakistan Today reported.
Posting the video of his cousin seeming to name Afridi as her killer, Zaheer Khan Burki wrote on Facebook: "We demand the quick capture of Mujahid Afridi and want justice for Asma bibi."
Protesters gathered in several locations across Pakistan on Tuesday to demand urgent action to locate and arrest Afridi.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
