First of all both cheated dutta in fact just hide their true face and show dutta a good and pretty woman
All seema need is money which leads her to her destruction though at end she helped dutta a lot but all for her mean that may be dutta forgive her and accept her and give her the previous life and a way to get out of that bad world she is living...yup she wanted him to forgive n accept her even though she knew how much tasha loved each other
On other hand supriya wants just her love Ravi and she is scared to tell dutta the truth because of his reputation but what she did wrong is that she play with dutta's feelings to have his faith on her and once again she broke his heart and made him not to trust people and love any lady and even break dutta and nakku's friendship leaving a letter behind..agree with u sups hurt him really badly she should have told him the truth instead , moreover she wasnt even regretful of her actions but somewhere nakku is also responsible for not telling dutta about the truth but her reason not to tell the truth is not to broke dutta's heart once again as sups is ready to marry dutta.
so for me neither seema is quite good nor supriya as they both play their game and use dutta but both are helpfull in bringing tasha close as sups leaving dutta leads to tasha's marriage and seema's re-enter helps to realize dutta about his love for nakku...good both of them moved out n made dutta realize the importance of true love in the form of nakku ..thanks for sharing ur views