super busy right now at work, so i only skimmed the first page. it's waaaay too long for me to get into, and probably moot for me to join in. so here's my crunchy opinion.
nurse whenever your baby wants, wherever your baby wants. i fully believe in "if it bothers you, don't look, but SIL's house, SIL's rules. also, i don't agree with "whipping it out". so it depends on how this OP's friend? sister? did it.....most women don't "whip it out", but the anti-bf people seem to think that's what they/we always do. i practice discreet nursing, as do most moms who NIP, out of respect for other people, and bc i really don't want my boob hanging out for the world to see, and i also know nobody really wants to see that. although it doesn't *really* matter if people want to see it or not, though, bc they can always turn away.
i sorta/kinda lost a friendship, when a friend's h asked me to not bf in the room at their party. i respected that, and just didn't go to the party...they were pissed, and we have hardly spoken since (they used to be our "best couple friends").