People...ugh...

What gives people (nevertheless, complete strangers) the right to make unsolicited comments about someone's baby?? My daughter was born at 32w2days, reaching her lowest weight of 3.5lbs. She's now nearly 6 pounds and over a month old. She was just released from the NICU and had her first pediatrician appointment. This was the very first time I've ever brought her in public, and some random woman in the waiting room says, "oh, that's BRAND new baby. She's sooooooo tiny!" And says some other stuff I decided to just ignore. Well..she's not BRAND new and she looks big to me considering her due date is still a few weeks away. I don't know why that bothered me so much. Probably because I feel like people shouldn't just make comments about other people's children when they have no idea what's going on in their lives. What are your opinions on that? I know my daughter is going to probably always be a little small due to being a preemie...so it's just unsettling that the unwanted comments are already starting.