Would you call of the wedding over this no matter how much it hurts?

I just found out the reason why my fiance's goddaughter won't let him babysit her daughter (his granddaughter) overnight. He has known his goddaughter since her birth and practically helped to raise her. She is 16 years old now with a daughter of her own and my fiance loves her dearly. He has been asking her for a while now to keep the child overnight but she would never give him a yes or no answer. She would shut down and not speak to him for days via text. Finally today he asked her why she won't let him keep her overnight and she tells him it's because she doesn't like me. I don't know what I have done nor said for her not to like me nor allow her baby over to the house. He and I have been dating for 7 years and are about to get married in October. It kinda hurts me to find out after all of this time that she don't like me. What do you say about this and how to respond to this semi-shocker! I almost feel like canceling the wedding because it's as if once I marry him, there are peopl in his family whether immediate or extended really don't care for me and the marriage may be doomed. What do you do? Granted I'm not put on this earth for people to like me but what I ever do to a 16 year old kid? I hardly see her. She has come to our house a few times before she got pregnant and has spent the night here. I just don't get it.