She didn't mention her ex by name, but it's pretty clear to us that this quote is about Ryan. "The logistics of being with another actor are challenging," she confides. "There has to be a real understanding of how you share your time, especially when two people's careers are going at the same rate. Or even if one person is more successful than the other, that also proves challenging. There may be a competitive thing."
So was Ryan jealous of Scarlett's success? We'll have to wait for the next interview to get more details!
This story has a happy ending though: both actors have found love again - Ryan with Blake Lively, and Scarlett with Romain Dauriac, a contemporary art dealer.