Bonezz,
I really feel you. My Mom went through a really rough time when my Brother got married a few months ago. His fiance didn't want my mom to even go to the wedding. She sent a letter to my Mom Basically saying she didn't want anything to do with my Mom except if my Mom needed help. My Brother called her and really wanted her to be at the wedding so she went for him.
I talked to my Brother other day and he said my stepmom didn't want my Mom at the wedding and even had talked to the Elders about it. They approached my brother and he said theysaid we could go but not reception. Your Daughter might be being pressured by Elder's. They like to push the knife a little deeper. Try to go if you can, I went to my brother's wedding with my mom. We even made up a little code if we were loosing it. I had to tell my Mom a couple of times during the wedding it's just one day, we are here for your son. I have never been so proud of my mom in my whole life. She sat there with dignity and grace. I hope you can go with someone who can be a support for you. Take care of yourself .