I can see why she doesn't touch this dairy topic. It is a confusing subject and lots of people don't really understand the differences between all the terms being thrown about. Classically, there is lactose intolerance and dairy protein allergy. Lactose is sugar that requires an enzyme, lactase to breakdown the lactose. People make less of it as they grow older so then symptoms might appear. Other people may not actually make that much but their gut bacteria compensates such that until the microbiome gets disturbed (with antibiotics for example), they are fine but after such an event, they also have symptoms. But if that microbiome changes back to the original form, their intolerance goes away. dairy protein allergy is allergy to milk proteins, symptoms are hard to separate from lactose intolerance but the age of onset and time course are totally different. "dairy sensitivity" is quite meaningless and food sensitivity testing kits is like reading palms.
She probably was lactose intolerant but didn't have a good response to Lactaid (it just doesn't work or is enough for some people) and so it was explained to her or she understood it as "dairy intolerance" and not lactose intolerance. the milk ladder didn't work for her or she could speed through because she didn't actually have a true allergy. Anyways this topic is kind of boring and I don't think it's bizarre that she doesn't want to dedicate time in a video going through it when the vast majority of her viewers probably don't care.