Here's an update and some questions.
Shortly after I noticed her feet, she started not always coming out to eat, which was unusual. I also noticed crusts in the corners of her mouth. I rushed her to the vet ER and they gave us antibiotics, anti-inflammatory and solution to clean her feet and mouth.
After the first 2-3 days she got better. And then she got really bad. She had diarrhea, bloating, gas and completely stopped moving and eating. I took her to the vet again and we agreed I should stop giving her antibiotics. Instead they gave me probiotic (which they should have probably done the first time!) and Critical Care. That second vet also said he felt something on the right side of her abdomen and took an x-ray. Later he called me and said what he felt was probably displaced organs due to bloating.
I force-fed her for a few days, during which time she seemed barely alive.
The probiotic and fibers finally kicked in and she she got better all of a sudden. With the antiseptic her feet got really pink and soft again and the crusts in the corners of her mouth disappeared.
She barely made it, but after an excruciating week for all of us, she finally seemed normal again - eating and moving and interacting with us. I also changed the bedding to GuineaDad and got rid of the shavings. They seem much more comfortable now.
And now I am getting worried again, because after the initial happiness of her recovery passed, I now notice changes in her behavior. She's eating and all, but she seems to have less control over her bowel movements. She goes (broken link removed) and (broken link removed) , while being in my wife's lap, something she's never done before. She poops A LOT more than usual, like making a small pile at a time, although the shape and solidity seems fine. Poop on the outside seems wet and color is very dark. And sorry about the graphic detail, but the corners of her poop seem to have something like a poopy string on each side. Like so:
Also, I might be imagining, but she seems a little bloated on her right side. I wonder if she developed intolerance to some of the veggies that I've been giving her throughout her whole life (4 years).
I use her sister for reference, and she's showing none of those things. I might need to take her again to the vet, but it's an ER and I don't think they'd consider this an emergency. Does anyone have experience with anything remotely similar?