This is a complicated one so TIA for reading and any advice is welcomed!!!
My fiance and I met in 5th grade and I was best friends with his twin sister. As we grew up (middle school and high school) we grew apart and were friendly, but not so close anymore. My fiance and I started dating our sophomore year of high school. His sister and I ended up going to the same university and have been in similar friend groups the whole time. She has changed a lot since we were little (obviously) so we are so different now! When we got engaged in October, she didn't seem excited at all and would actual say negative things about weddings and getting married around us. This past month, we have been choosing and asking our wedding party and we asked her to do a scripture reading at the wedding rather than be a bridesmaid. This decision was made for many reasons but the main ones are: we had grown apart, she didn't seem to be interested in participating in bridesmaid activities, and she had a different but important relationship with both of us (twins/old friends). Yes, I didn't want her to be a bridesmaid when I have much closer friends, but we also made that decision based off of what we thought was best for her personality and interests.
Long story short, we found out from my future MIL that the twin is super upset and "hurt" that I didn't include her. When my fiance talked to her about it, she basically said she understood our reasons but was still hurt. She doesn't know how we could fix it AND she doesn't really approve of the marriage because she doesn't like me (she thinks I am mean and she doesn't like the way that I handled a situation with a mutual friend who is battling severe depression). She thinks that her twin deserves better and doesn't want me in the family. This was obviously so horrible and painful to hear. I knew we weren't close (why I didn't include her in the bridal party) but I never thought that she thought I was not a good person or that she was against our marriage. Now I feel like I have two options - I know both of them will hurt in some way but I can't decide which one is better:
1. We could leave her as a reader and deal with all of the other family (MIL, FIL, etc.) who will be confused and disappointed and potentially hurt that I didn't include her in that way. The MIL has already confronted my fiance about this and I'm 100% sure that she will not be the last one. We don't want to include her more so this is a pro in that aspect but she would get to continue complaining and others would be upset which would keep coming back to us.
2. I can add her to my list of bridesmaids - bringing me to a total of 6. She wouldn't take any of my close friends out and would get what she apparently wants, meaning that she theoretically couldn't complain to others or bash me. This could be seen as a nice gesture and then maybe she won't think I'm so mean - we've really been thinking about her and other's feelings so much through this whole process. I want her to like me and I don't want to hurt anyone but a huge con is that she doesn't support the wedding. That hurts so much and I know there's nothing I can do to change her mind with my words so I just need to deal with this and be the best person that I can be. Hopefully she will see that soon.
Thank you so much for reading all of this and really any advice or comments would help a ton. 
P.S. My wonderful fiance is totally on my side of things and wants whatever will make us the most happy overall.
