Fiancé brothers girlfriend

So iv been with my fiancé for over 5 years. His brother got a girlfriend I want to say about a year in a half ago. We are not that close, we don’t text or hangout together if we do hangout it’s with my fiancé and his brother. Recently my fiancé told me I should have his brothers girlfriend in the wedding. I’m stuck between having her or not because she’s not a close friend of mine but my fiance thinks it will bring me and her closer together. Me and her get along we don’t have any problems with either other. Am I wrong to not ask her to be in the wedding even if we are not that close ?