So, bringing her along to shop for your wedding, making her your bridesmaid (effectively making sure she sees the entire damn thing) and then having the audacity to tell her that you knew her feelings all along after the wedding. And this is all supposed to be ok because you feel the same way ? Lmao. This is essentially emotional torture of the bridesmaid. There is a difference between sad/angst and straight up cruelty.
Well most of them are unrelated, aren't they? She wanted her there as her because they're obviously very close. And really what would the alternative be? "Sorry you can't come, can't explain why." Had she said anything before it would had just fanned the flames, and had she not said anything at all it would just have left the bridesmaid with a ton of what-ifs.
They both wants what is best for each other more than what is best for themselves, which in many ways makes it a better if sadder love-story. Kindness isn't always the best decision. "I know you loved me and I love you too, but I went through with the wedding anyhow. That is how resolute I am in my decision." A firm answer, a firm resolution. No what-ifs. It is sad, it is perhaps even a bit cruel, but it had to be done.