Boomer Grandma constantly buying junk food

So I live with my Mom and Grandma, and my Grandma is thoroughly a Boomer. I've made a number of posts before about both her and my Grandpa because... they're just very hard to deal with, and between them they meet literally every Boomer stereotype.

I'm mostly making this post because I think I may have found a cockroach in our kitchen for the first time, and it's likely because of my Grandma's food habits. I've never seen someone buy so much junk food in my life, and often it ends up getting left out, or thrown into our trash half-eaten. She primarily eats fast food, and every time she goes to the grocery store buys mostly candy, cookies, and pastries. She almost-exclusively drinks soda, and often will barely eat dinner but then subsequently have like 6 Chips Ahoy cookies as soon as she throws out her plate. The other day I saw her come home with a coffee and donuts and immediately dump a shitload of sugar into the coffee, and down like 3 donuts all at once.

Also, relatedly, she refuses to use regular plates and cups, and instead will only use plastic cups and paper plates. She claims it's because it makes less dishes (even though she's not even the one who does the dishes). But all I see it do it create a TON of extra trash.

And alongside all of this, as I said she doesn't store her food well either. There's half-open packages and stuff around, and I'm pretty sure she hides food in her room too because my Mom will often get onto her about her eating habits (especially because a doctor told her she's diabetic but she refuses to listen).