I think it might be Padma Purohit

1. Radhika and Dev never becoming one - Rohan will get Radhika, while Barkha will get Dev

2. Rohan getting RajPurohiti and all respect in society.

Padma is insulted and betrayed by her own husband and Chayya and Dev. Dev has practically everything whatever Rohan wished for - RP and Radhika more importantly. She asks Rohan before throwing him out - what did you think, you will keep her against her wishes? she cannot support her son in public, so hence the backdoor. Also when the truth of Chayya came out, she felt insulted and cheated. She felt that everything was lost for her. So she wants to make doubly sure that Dev does not repeat the same thing for her son. And she found her ally in Barkha. Couple of things on ME - she says to Radhika to go from Southside door and couple other things. These all things point that she is playing her cards very closely and carefully. Not want to take a chance and expose her game. Because she cannot win openly, she is resorting to this tactics.

Having said that I want to say that I feel that it is not Padma. Because though she is insecure, I do not want her to be negative. I especially like the actress playing Padma and Barkha alone is enough for being negative. It should be Dai Amba or anyone but not Padma.