Alexandria Ocasio-Cortez, 31, was ridiculed on stage by Trump on Monday.
Trump mocked her environmental proposals and questioned her education.
'She did go college, right?' he asked the Pennsylvania crowd.
Ocazio-Cortez, a 2011 graduate of Boston University, replied: 'Plenty of people without college degrees could run this country better than Trump ever has'.
Donald Trump has mocked Alexandria Ocasio-Cortez's qualifications, asking the crowd at his Pennsylvania rally on Monday afternoon whether she had been to college.
Ocasio-Cortez, 31, is a perennial target for the president, who frequently attacks her left-leaning policies.
On Monday, talking about her environmental proposals, which Joe Biden is partially incorporating into his own plan, Trump again repeated the figure of $100 trillion to estimate how much the Green New Deal would cost - a figure the Democrats say not accurate.
'We'd lose a fortune at $100 trillion,' said Trump.
'Made up by AOC plus three,' he said, referring to 'The Squad': Ocasio-Cortez, Rashida Tlaib, Ilhan Omar and Ayanna Pressley.
He added: 'A great student of the environment. I don't think she ever took an environmental course in college.
'She did go to college, right?'
Ocasio-Cortez graduated from Boston University in 2011 with a BA in International Relations and Economics.
She said his words were 'classist and disgusting'.
The New York congresswoman replied: 'I could say yes, but who cares? Plenty of people without college degrees could run this country better than Trump ever has.
'As much as GOP cry about “elites,” they're the ones who constantly mock food service workers, people w/o degrees, etc as dumb. It’s classist & disgusting.'
She continued: 'I've hired people w/o degrees who have done incredible, effective, & strategic work.
'The more college costs soar, the more degrees become a measure privilege than competence.
'Our country would be better off if we made public colleges tuition-free & cancelled student loan debt.'
Trump graduated from Pennsylvania University's Wharton School in 1968 with a BA in economics.
Donald Trump Jr also graduated from Wharton, with a degree in economics in 2000.
Ivanka Trump attended Georgetown University for two years before transferring to Wharton, from which she graduated with a bachelor's degree in economics in 2004.
Eric Trump did not to attend Penn, instead graduating from Georgetown with a degree in finance and management in 2006.
The president has a long history of ridiculing Ocasio-Cortez, the youngest woman ever elected to Congress.
In April 2019 he called her a 'young bartender' during a fundraising dinner for the National Republican Congressional Committee.
After college she interned in Senator Ted Kennedy's office, and became a community activist.
Before university, Ocasio-Cortez was a high school student with an interest in microbiology and space.
She won second place in the microbiology section of the Intel International Science and Engineering Fair.
In a show of appreciation for her efforts, the MIT Lincoln Laboratory named a small asteroid after her: 23238 Ocasio-Cortez