Your'll are forgetting that Nands is making a very big sacrifice so that Tanya is not left alone at this stage..
She may be married ot Aseem but they do not have a Husband wife relation...She left Karen 20 yrs ago only so that TAnya is not left alone with Manthan...
If she had come back, TAnya would ahve had to leave....becos Karan only loves N...
If K and N were separeted in the beginning its only becos of TAnya...
Anybody who has watched Kyunki from the beginnig will agree that K and N deserve each other...
Even today, T should give a divorce ot K and move on..she will know how much N suffered by being away from K.