"Did you have any hints that there was a problem?" Letterman asked her.
"I don't want to go into the specifics," said Hathaway, who appeared on the Late Show Tuesday night to promote her film Rachel Getting Married, "but I will say that you do have to give me credit because as far as relationships crashing and burning goes, c'mon, I did pretty great. I mean, scorched that earth!"
Pressed further by Letterman if Follieri was in jail, Hathaway asked him, "Do you want to know his shoe size, too?"
The Devil Wears Prada star revealed that her relationship had ended months before Follieri pleaded guilty Sept. 10 to 14 counts of wire fraud, money laundering charges and conspiracy.
"We were over for a bit. There were conversations afterwards, but the relationship was absolutely done," she told Letterman.
However, the actress, 25, is moving on from her breakup by shedding her old self.
"I quit smoking," Hathaway said. "I quit for a while and then it was a stressful summer and started smoking again. But I just quit."
Hathaway says her public breakup was the perfect time to make other changes in her life. "I quit drinking and I also gave up meat and fish and fun," she said.
Despite all the heartache, Hathaway assures she is doing fine. "I'm very happy. I'm in a good place."