Mil issues

So today we came home and my mil was coming home at the same time. We live with her. My son who is three was walking towards our gate and she said “good evening” he didn’t say anything back. I tried to get him to say something but he is somewhat shy. Especially to my husbands family. Even though we live with them, they barely interact with him. Anyways he didn’t answer her and she got upset saying if she didn’t have something to do he would stand outside till he answered her. This made me upset because 1. You barely speak to him and 2. Your not going to make my three year old stand outside on a sidewalk till you say it’s okay to come in his house.

Any opinions ?? She makes me really upset and sometimes Hubby just sticks up for his mother