Mother in law issues 😠😩

I live with my mother in law and she continuously says,"fuck the doctor." She gave my son prunes today because she believes he needs them because he has trouble pooping. He cries every time he poops. He's been like this since he's born. I ask at every appointment and the doctor says he's just learning to poop and he'll grow out of it. Well my mother in law did not take that as in answer. I don't know what to do, my son is two months and 14 days old and he had puréed prunes. She also wants to give him water. I'm a first time mom. Will my son be okay since he ate solids so early? And any advice on what my husband and I should do? Thank you!