Honestly I doubt she'd even be told to use metformin. She's showing pretty advanced signs of diabetes and I doubt metformin would help much. Though it might cause her to lose weight, it's a notoriously aggressive medication for side effects. It might be a repeat of how she got sick from feces lake. She'd just shit and vomit out a few dozen pounds before quitting metformin.
Also it's not true you put the w eight on when your sugars are controlled because of carbs and sugar. It's because your body is suddenly going 'Hey wait a minute, we can like, properly process food now! Lets make it into fat!' There is likely a medical term for it, but that's basically the body properly doing things. Most people don't bother excercising etc to counteract the body suddenly working right. Which..well we know Hamber won't.