The attitudes are the important thing to address, but my immediate thought is a practical problem: if people are upset about eating snacks which are sort-of-someone's but also sort-of-communal can people please have a box or a cupboard or lockable something for THEIR snacks which people actually respect? And Kaylee can snack on whatever SHE wants, and Blake can snack on whatever SHE wants, and Blake not get upset because too much of the wrong food is what's available?

it had already made activities she previously enjoyed, like biking, a struggle for her

I'm also quite torn. Anti-fat attitudes are incredibly prevalent, so massively judging people for eating is a gigantic problem and usually makes things worse. But "eating a bunch of snacks that actually don't make you feel good" I think is something that can be not-so-good, and finding alternatives can be good (but like, not if it doesn't seem to be a problem, and not at all costs..)