Gauri's obsession is understandable in "Indian Television World" but not in real life. Like all obsessed women of T.V. Gauri thinks that it's Kali to be blamed and not Yug, not to forget, its Indian MCP thinking that women are wrong.
Also, her upbringing is wrong. Kalyani made sure that Gauri grows to be a selfish girl, who hardly has feelings for someone else. She has made her ruthless. Madhuri, though, didn't do anything for her daughter, got influenced by Kalyani and encouraged her to do things to separate KaYu (since she also had to go through the same)
Not to forget, Gauri has always been selfish. I mean, you can't expect a girl to sacrifice the guy she is obsessed with for someone who she doesn't really care, if she is ready to bury her father alive.
I think, here, the biggest fault is Kali's. From childhood, she has sacrificed for Gauri. Her identity, her voice, her feelings, the praises she deserved. So now, Gauri wouldn't possibly think that Kali also loves Yug and even if she does, Gauri knows tat Kali will sacrifice him for her.
Gauri's obsession would have been under control if Manjiri had been there with them from childhood. Alas, that didn't happen. Also, if she knew about Kali-Yug's bond from before, there were high chances that she would have accepted them.
P.S. totally my thoughts. No offense to any fan of any character.