Am I in the wrong?

My sister is a free range parent. She doesn’t make her kids do anything they don’t want to. They go to bed after midnight, sleep until noon typically, eat whatever they want whenever they want, even if that’s cookies all day. She thinks if they get sick from it then that’s a “natural consequence” and that they’ll learn from it. I recently texted her about her 6 year old starting kindergarten this fall. I’m an elementary teacher so I was excited for him. Well, this is how the convo went. For reference, we typically bicker like this. We’re twins. We do love each other but we’re very very different despite being twins.

I used to not care much about her parenting practices because they were so young but now I see how harmful they can be. Should I mind my own beeswax or should I encourage her to seriously send him to school?!