Agree the store behaved badly but honestly why would you want to bf in there? Our local store is so packed with stock you can barely move, it's dusty and dirty and dingy. The 'bench' she was sitting on must have been in the (too small) shoe trying on area and I expect the shop was full of fraught parents buying back to school trainers etc.
I think I would have been pleased to have an excuse to escape the madness of the place and gone to a nearby cafe instead.