Few details have emerged about Tashfeen Malik's life in Pakistan, where she lived from 2007 to 2014 before heading to the United States on a fiancee visa.
Malik studied pharmacy at the Bahauddin Zakariya University in the central city of Multan, where she got a degree in 2013.
She also took classes at the Multan branch of Al-Huda International Seminary, a women-only madrassa with branches across Pakistan and in the US and Canada.
The region where the school is located, however, is home to thousands of extremist seminaries, with hundreds linked to al-Qaida and the Pakistani Taliban.
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Pakistan, which supports Islamic militants battling archrival India in the disputed region of Kashmir and is widely believed to have ties to insurgents in Afghanistan, has long turned a blind eye to institutions that teach radical interpretations of Islam.
Al-Huda said in a statement that it has no links to any "extremist regime" and seeks to promote a "peaceful message of Islam and denounce extremism, violence and acts of terrorism."
"It seems that she was unable to understand the beautiful message of the Quran. We cannot be held responsible for personal acts of any of our students," the statement said.
Malik spent more than a year at Al-Huda, taking classes six days a week, the school's spokeswoman Farrukh Chaudhry told The Associated Press.
She enrolled in a two-year course to study the Quran, its translation and interpretation, but did not finish the course, Chaudhry added.
Malik was a student there from April 17, 2013 until May 3, 2014, when she handed in her last paper in the first-year curriculum, the spokeswoman said.
Chaudhry said by phone from the southern port city of Karachi, where she is based.