You need to grow up. It's one day and it's not your day. You're not paying for it, you're invited to it. If you choose not to go, you will damage your already shaky relationship with your sister. She may not be the smartest, most mature, or least spoiled person you know, but she IS your sister. And as the eldest, you need to act like the eldest, put your big girl panties on, smile, and go to the wedding without your daughter. If you don't, your sister may never move past this and I wouldn't blame her.
Your daughter will move past this when you do. So for your daughter's sake buck up, accept what you cannot and should not try to change, and do the right thing. Your daughter needs the stability of a normal family relationship, not the drama of a day's disappointment to cloud her closest relationships.
This isn't rocket science, this isn't the life or death brigade, it's a wedding. It's a day that will be put to rest like the 20,000 or so you have already witnessed. So stop the dramatics and move on. Your family will thank you for it.
Your daughter will move past this when you do. So for your daughter's sake buck up, accept what you cannot and should not try to change, and do the right thing. Your daughter needs the stability of a normal family relationship, not the drama of a day's disappointment to cloud her closest relationships.
This isn't rocket science, this isn't the life or death brigade, it's a wedding. It's a day that will be put to rest like the 20,000 or so you have already witnessed. So stop the dramatics and move on. Your family will thank you for it.