Naureen Leghari, a second-year student of the Liaquat University of Medical and Health Sciences in Jamshoro, Sindh, had visited Syria to join the ISIS terror group in February, the Dawn reported, citing sources.
She had also received training in Syria for using weapons, the sources added.
Naureen came to Lahore about three weeks ago and was being tracked by security personnel. She had reportedly been contacted by militants through social media, the paper said.
Security personnel found her college card and her father's computerised national identity card from their hideout and reportedly contacted her family in Hyderabad.
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She was being interrogated about the modus operandi of the militant network and other people associated with it.
Security forces said they foiled a "major" terror attack on minority Christians ahead of Easter in Lahore and killed the militant and arrested his two aides, including the woman.
A committee was formed by the university to investigate Naureen, the paper said.
"She [Naureen] was in contact with a boy on social media for quite some time," the vice chancellor said.
"[Her contact with the boy] transformed her mindset and influenced her towards extremism," he added.
The vice chancellor said that Naureen was a "reserved girl" who used to "pray five times a day."
Sheikh added that two of Naureen's friends were Hindus.
An official said said that after reaching Lahore on February 10, Naureen had messaged her brother through a friend's Facebook profile that she has reached the land of Khilafah (caliphate).
Prof Abdul Jabbar, father of Naureen, had filed a missing reported of his daughter on February 10.
A source in Lahore police said she was connected with the IS men on Facebook where she took allegiance to the IS chief.
Facebook had blocked her account because of her extremist views.