Re: Bridesmaid while breastfeeding - am I stressing for nothing.
I wasn't in a wedding, but went to a wedding with our 3rd when she was 7-8 weeks old. I wore a strapless dress and strapless bra with pads (I hate nursing bras anyway, so switch to regular bras with pads once I got back down to a somewhat reasonable size), threw a blanket over my shoulder and just pulled my dress down in the front. I would also stick a burp cloth over the top of your dress so you don't leak on it.
It will probably be a bit of a pain in the butt, but not the end of the world. She'll need to understand that you will need to excuse yourself (or just be unavailable) at certain times during the reception to feed the baby.
I would have someone specifically assigned to keep an eye on and help your daughter, and another person to be with the baby, and then you can jump in and help as needed, but not feel like you are being pulled in 3 directions at all times.
Hi I'm Sara mommy to 3 little Mischief Makers