I don't see any love between Keerti and Sunny. It's more of an emotional dependence. Sunny is an escape from the toxic environment of her home where her mother hates her brother. On top of that he Sunny somewhere is similar to Raghav (in Keerti's eyes) whom she is forced to hate due to circumstances.
The trauma she endured in her childhood has twisted her psyche in a way that makes her seek solace in a despicable man. Though she is insufferable now all her actions stem from a deeply troubled childhood. Seeing your father and brother getting lynched can mess up your mind.
Until they lived separately she had responsibility of her mother which kept her grounded to an extent. Now she doesn't need to act mature and she is freely acting on her emotions.
I hope makers address this issue in coming episodes. Hopefully it won't go unaddressed like her feelings in MMS fiasco.