Don't you wish at the time you would have come up with something to put her in her place? I think if one mom (in her case it might take more) stood up to her and said
"How would you know how many feeds my son needs? As noone knows how much milk he has each feed nor how many calories are in each feed, how could you possibly know after 5 minutes how much he needs.

As for sleeping through the night seriously? How many babies are actually sleeping through the night at 11 weeks? Not mine.

I am mad for you! You just want to say "Weigh my baby and keep your opinionated comments to yourself. If he is gaining as he is supposed to and is healthy then.......Shut up!