doubtful babe. the only logical thing i can think of (i.e. after reading today segment wu) is that she knows till what extend yash went (and segment show he was arrested, hasnt died) thus just thinking that if he can take away her mother he can do harm to sid as well, she may break her ties with Sid just to secure him - that's the only thing i can thnk of.. and covering it with statements where making their love story respnsible for all mess. but still why new identity and back to india?
but let's see.
It would be much more reasonable to come up with something like that. Nia also hinted towards something like that; Roshni blames their love story for all the problems created to her family and Sid, and thus wants to stay away from all of them in order to protect them. And since she broke all ties with Sid, a completely new identity is used because Roshni is and always will be attached to Sid both emotionally and physically.