In my opinion she wasn't having a dig. She was pointing out just because a child is different doesn't mean you have to highlight it further by dressing them in a fashion that would single them out.
How many people do you know who dress their children - disabled or not - in a way that singles them out?
Personally, I don't know any and as for dressing them like pensioners -
and I think a parent would have to be a bit odd or eccentric to do so. My sister bought my grandson a tiny flat cap, but that's a bit of a family joke as my late father used to wear one. Is that wrong?
When I went to school back in the 60's there were many children who were poor and dressed scruffily, but that was then - we've moved on now, and very few kids go around poorly dressed, so there was really no call for her remark at all.