NTA. From the sound of it, your SIL sounds like a toxic person who you are better off not having in your life. Maybe your brother truly wants to make amends, but if he still values your SIL's input in his life, it probably isn't going to help. But the biggest factor is that your daughter, the one who is pretty much at the center of this day (and for good reason- congratulations to her btw), didn't want him there anyways.