Angad is using Mishty to teach Kartik the lesson of his life. Zeib is snatching Kartik's love interest and returning his due with interest for all the harm he did to Angad.
He is probably aware of the fact that Prithvi is behind Josh's murder to get Kripa and hence has come out of the jail with the help of the police and his lawyer Shabbir. So, he is using Mishty to put chilli powder in Prithvi's eyes, by which he will not bear the pain and yell (probably yell out the truth to the world).
He is also aware that Kripa and Prithvi are married legally, but Kripa is still his and will always remain his. So, he is making her feel jealous by using Mishty and follow him, so that he gets to be in her presence most of the time and keep a check on her mind even when he is away from her. So, Prithvi will become more and more despo and will fall in the trap while negotiating one more mistake. He is already arguing with Kartik and in the heat to save his sister's interest he may blabber the truth.
But, when Kripa learns the truth, she will collapse like a huge Banyan tree, because she thinks that Prithvi is a very nice person and a very good friend. If at this time she is not supported, she may become mad and protest to believe anybody in her life.
On the other hand, Mishty is considering Kripa to be her compition for Zeib. She is trying to keep Kripa in her limits of married life. But, I have a feeling that when she thinks that she is failing or has failed, she will harm Kripa with the help of Zeib (probably accused of a crime) and send her to jail also so that she is no where near Zeib.
Even now, I feel there is a plot to keep Kripa away from the place (she being at Nainital like she was fooled when Angad was engaged to Mishty), when Zeib and Mishty will have no resistance from Kripa so that the harm/intimacy growth rate can be accelerated.