My SIL view on stay at home mum

I am a stay at home mum I have a 20 month old and a newborn my husband works 6 days a week and his sister said to me "I can't wait to be a stay at home mum then I can just stay home all day and sleep and watch tv" I laughed and laughed and laughed and then hung up on her 
By the way she doesn't have kids