Two wrongs never make a right. There is no doubt both loved each other but both choose family happiness yes it was dev who first choose his mother happiness and I am sure if situation reverse sona will also choose her family happiness. Dev didn't loved her enough to fight for his love and sona didn't loved him enough to wait for him. And I am sure this triangle help both dev sona how much they love each other what extent they can go to stay together.
To wait for Dev.Sona need one solid reason.Love is not enough to wait.If Dev give that solid reason.Sona can wait for him.Dev has conveyed what he wanted.He wanted break up n break up happened.Why would Sona wait.When she is convinced that for Dev his mom is imp n he will select her happiness over anything.So there is no point in Sona waiting all her life.Hurting herself n her family.