How do you deal with people or parents that compares their little one to yours?

It depends... If she seems worried that her little one is smaller in size, I will reassure her that every baby is different and must look at mummy size! I'm fat, you can't expect my kid to be small and scrawny right? So likewise if she is being mean that my kid is fat, I'll just laugh it off and say yah, my milk too much fats! Just take it with a pinch of salt. Give support when needed, and if it's a good Friend, laugh off the comparison, and if it's some random people, answer with a hint of sarcasm... :x