Lazy writing. Main characters seems to have serious mental illnesses and need psychiatric help. Not being sarcastic. Deepa is so emotionally abused that she supports her abusers whole heartedly. In real life that could be the justification of this destructive behaviour. But as an Indian serial, it's safe to say lazy writing and probably the ideal that the serial wants to show is desirable.
Plus the antagonist has serious an unnatural phobia of black color on people. She needs help.