It seems as if Su has forgotten the kindness shown to her by Pratharna. Initially she was just a miserable women living on ant-depressants. Now it seems she is so loyal to Rio who didnot even want to give her second look at one point.
Just goes to show how ungrateful people can be. I hope that Mohini marry's Akshay and then begins to give Su a hard time, then she might release how valuable Pratharna was and go running to her for forgiveness.