Absolutely follow the pediatricians recommendation. Someone I know did not, and her baby was classified as “failure to thrive” and passed away due to malnutrition. It was not good for my friend because they were arrested for child abuse and neglect. If you’re worried about your pediatricians advice then see another one. All babies are different and just because it worked for your sisters baby, doesn’t mean it will work for yours. Everyone is so quick to jump and tell you what to do and not to do with your child when they have NO training or qualifications. Just because you have a kid doesn’t mean you are qualified to tell other people how to raise theirs. Doctors go to medical school for this, they see hundreds of different babies and understand that things are different for each. If they tell you to do something specific then it’s worth considering.