I think their are some people here who need to get off their high horses and stop for a second and consider the position that the bride is in.

Consider how she must feel having to even ask this of her future SIL? She must have some ultra conservative people who she knows will get highly offended and upset if she has decided that this is the avenue she has to resort to. Imagine how she would feel on her wedding day when she is trying to relax and be happy if instead she had to be on edge and nervous that people were getting upset or even possibly angry about something. I know as a bride I wouldn't want that and I would want to minimise the possibility of this happening. She has done that in a discreet and reasonably polite manner. She hasn't shouted it from the rooftops, she hasn't gotten angry or made a scene, she has simple made a request and outlined her reasons behind it.

Get over it people. Life is not just about breastfeeding. Your child and you will survive if for one day you have to cover up. Your family relationship if you don't may not.