I'm rolling my eyes at the 'psychoanalysts' on this thread. What is it about a difference of opinion that you're so afraid of? Why does everybody have to feel the same way about breastfeeding or anything else? I don't see very many b/f exhibitionists, very few and far between. That's probably because the vast majority who breastfeed just get on with it, discreetly, as is their choice.
I completely disagree with posters who've suggested that the OP's sister is a tremendous advocate for breastfeeding, she isn't, not in my view. It's not abnormal to breastfeed, it's completely normal, nothing magical or mystical about it. To me it's private between mother and baby, no room for onlookers and certainly no need to 'make a point' of showing anybody else.
I don't understand why, when all of the posters on these threads always say that they are discreet, or barest flash is all that is seen, are so up in arms - the thread isn't about you. It's about OP's exhibitionist sister and how uncomfortable sister made OP feel. Valid feelings, whether you agree with the content or not. It's the disregard for any view other than "If you're breastfeeding, you need have no feelings for anybody else, if you make a performance of it and draw attention to the marvellous, magical act, that's all to the good, it will make more women do it". Absolute rubbish.
I personally don't like the 'gobbling' noises, but I wouldn't tut or give a look or do anything else, I would completely ignore it so why am I not free to feel what I feel? I don't like hairy toes either, they make me feel a bit sick... some people don't mind.
I don't believe that there are as many 'disapproving' people as commented on in these threads, any more than there are many exhibitionists. Nobody cares or is in the slghtest bit interested, they don't want their space encroached on, nor be 'forced' to see anything (not just b/f'ing) that they don't want to see, they just want to be in their own little 'bubble'. People seem to generally be tolerant if the society 'niceties' of not bothering other people (about anything) are met.