Those words will surely haunt Sona and will remind her of all the promises she made to herself and Dev. She will recall how she accepted him with all his flaws. She might be angry initially but she will melt for sure. Dev was the perfect boyfriend. He never gave her a reason to complain, loved her immensely and respected her. And being a very sorted girl, she will not take this on her ego.
It's always good to look at the brighter side. Every person has a dark side but doesn't mean he or she is bad or evil. Sometimes people do say things in anger or while going through emotional pressures but they don't really mean it. Come on, everyone of us must have said or done things in anger to their partners but don't we regret it later and patch up. Don't we just say things just for saying but never actually mean it. We are all humans and so is Dev!