Tashfeen Malik, 29, studied at the Al-Huda Institute in Multan, which targets middle-class women seeking to come closer to Islam and also has offices in the US, the UAE, India and the UK, the teacher at the seminary who gave her name only as Muqadas said.
The institute has no known extremist links, though it has come under fire in the past from critics who say its ideology echoes that of the Taliban.
Malik and her husband Syed Farook, 28, went on a killing spree at a social services centre in San Bernardino, an act praised by the Islamic State group who hailed the couple as “soldiers” of its self-proclaimed caliphate.
Investigators suspect that Malik, who went to the United States on a fiancee’s visa and spent extended periods of time in both Pakistan and Saudi Arabia, may have radicalised her husband.
The probe is trying to establish if she had contact with Islamic radicals in either country.
“It was a two-year course, but she did not finish it,” the teacher Muqadas said.
“She was a good girl. I don’t know why she left and what happened to her.”
The teacher did not say when Malik studied at the seminary, but fellow classmates at the Bahauddin Zakariya University said she had attended the madrassa after classes at the university, which she attended from 2007-2013.
An administration official at the academy in Multan said he could neither confirm nor deny that Malik had studied there, and said he would discuss the issue with management.
“But we have nothing to do with it (the shooting) and are not responsible for our students’ personal acts,” he added.
One of Malik’s former classmates at the Bahauddin Zakariya University in Multan, where she studied pharmacology, told AFP she had attended the madrassa after classes, saying she “drastically changed” during her time there.
“Gradually she became more serious and strict,” said the student, requesting anonymity.
A second university student who also requested anonymity confirmed the account.
Pakistan has pledged to crack down on religious seminaries suspected of being breeding grounds for intolerance or even fostering extremism, with the country’s information minister Pervez Rashid terming them “universities of illiteracy and ignorance”.
However the government’s efforts to rein in madrassas have prompted anger from many clerics who accuse the authorities of maligning religious leaders in a bid to build an “anti-Islamic narrative”.