Having listened to her rant on for hours and hours in the past about her friends little boy who was ...oooh.. so naughty and destructive and who never did what he was told...while her little girls were soooo good. And why couldn't her mum control the little boy???? I would gently try to point out the sometimes little boys don't behave like little girls - I had one of each at the time. Now she has a 2yr old little boy and he's naughty and destructive and never does what he's told....and her other children were sooooo good at this age.
I just frown and nod and make sympathtic noises and tell her that boys can be like that.