MIL problems

My spouse and I are choosing to do a gluten free diet with our son. We should not have to explain why, but everyone feels the need to ask. It’s our decision as his damn parents what we want to do with him. My dad has celiac disease and so my son has a high probability of having it also. My dad suffered for a long time because it took so long for him to be diagnosed with it. I watched my dad almost die from it and I will not watch my son go through the same pain. We will be eating gluten free too.

Anyways, the point of all of this is my MIL. I explained this to her and she agreed with us on it. However, a few days ago she made a FB status saying “i’ll dress him how I choose when he’s in my care...just sayin. kids love french fries & chicken nuggets lol” (note: she shared a ad for some kind of baby clothing). This really angered me. We JUST told her about him being gluten free.. chicken nuggets are NOT gluten free!! And my son will NOT be eating any kind of junk or fast food. I want him to be better than me and be healthy. We will make exceptions for CFA when he gets older, but very rarely. I just don’t understand why she would make these comments when she told me she wouldn’t interfere with how I parent because people did it to her & she hated it.