On Friday, Fiorina responded to Trump's comments from last week that she was, essentially, unqualified to be president because of her face.
"Ladies, look at this face," Fiorina, echoing Trump's insult against her, told the National Federation of Republican Women at an event in Arizona Friday night. "This is the face of a 61-year-old woman. I am proud of every year and every wrinkle."
Trump's comments came in an interview with Rolling Stone, in which he was quoted as saying about Fiorina: "Look at that face! Would anyone vote for that? Can you imagine that, the face of our next president?!"
Trump and Fiorina, the former CEO of Hewlett-Packard, are both political outsiders in the campaign, having never held elected office. Fiorina is also the only woman seeking the GOP nomination.
The two rivals will next square off in Wednesday's Republican debate. Fiorina was not invited to participate in the first primetime GOP debate, but has since garnered enough support to debate against the more well-known candidates.
Watch Fiorina's full speech here: