Please help my brother's neglected piggie!!
So, about 3-4 years ago, my mom bought
me and my brother two female guinea pigs; an American (mine, I named her briefly Starlight, then permanently Scarlet after a couple months) and an Abyssinian (my brothers', he named her Millie) My brother had decided that the amount of hay his piggie left alone was unacceptable and waited until Millie ate all her hay before giving her more, (I and my mom did have to give Millie hay in several times). He also did not clean her cage well, so during the first year and a half or so, there were red miniature bugs in her cage from him not cleaning her cage well- Scarlet could've also had what I think were lil mites, but I dont think I noticed them unlike in Millie’s cage. we did have to separate the piggies in the first year because they didn't get along well.
Fast forwards to now, Millie is in my care now pecause brother finally relinquished ownership after I told him that he needs to either spend more time with his piggie or dad was probably gonna sell her in the upcoming move (he's threatened to do so once or twice because we hadn't interacted with them much recently). Millie feels like more bones than fat under her abyssinian fur, and I'm worried she might have a permanent hunched back/butt, she's had pooping problems for perhaps years now and I don't know how to fix it. I can't even figure out from the internet articles if an abyssinian's back is supposed to be raised while standing normally; only that it's a kind of pain response? Please help!