Kakul will not forgive Samaan - she will do the thing that she is thinks is right - she will tell Samaan to stay with Vanshika for the sake of their baby. Vanshika will probably make her feel guilty too.
Then, Kakul will start to know this other guy - when they decide to marry, then the truth will come out about Vanshika not being pregnant.
At that time, Kakul will have to make a choice between the other guy and Samaan. I think when she finds out the other guy only wanted to get close to her to get to Amarnath, then she will be with Samaan.