Get her to a small pet expert vet ASAP!!!!! I've had 6 guinea pigs in the last 10 years. As soon as they show any signs of sickness, its not long till there's no turning back. And I'll worn you now its gonna cost just as much as it does your dog or cat. Good Luck I hope everything turns out well. Also I would separate them if they aren't already so if she is sick they both won't catch it. My last two cavies both died from upper resp. infections all within two weeks, I took them to the vet and got meds and it was still to late.