There is no way that Kanya can get with Chunnu, no matter how anxious she is for her marriage to end.
Here's a few reasons why. Feel free to add more or counter these:
1. Kanya's parents obviously care about samaaj and have traditional values. Kanya will never go against them. I don't see Pammi and Anand giving up on RanKan relationship. And if they want this couple to continue their relationship, then Kanya has no choice.
2. Mallika loooooves Kanya. Because she thinks tht its because of Kanya that Ranbir will find himself. Ranbir cannot refuse his mom. And mommy will never consent to a divorce. Ranbir will try to either think up of something outrageous, or will be secretly glad of her insistence (when he does fall in love).
3. Pammi and Anand respect Ranbir alot. No matter how much they love Chunnu, Ranbir will always be their son-in-law. I don't think that they will ever agree that RanKan match is not made in heaven.
Just my thoughts on why Chunnu and Kanya relationship will not work.