Happy to hear that Nikki is doing better. Rat poison will affect your animal immediately. Chances are she got into rat poison when she was roaming around. Lots of people that don't have dogs use it. I'm also surprised that your vet sent her home without supportive care. She should have been treated around the clock until she was eating and standing on her own.
Great!! I am sooo happy for you. Sorry I hadn't left this on the last post but if the color return in 3 sec or less she could be anemic. The color of the gums is also an indication.
Excellent news! Congrats! Inspect your yard and the surrounding area for D-Con and other types of rat poison. Ask your neighbors if they had any recent pest control specialists come around. This is why I never ever use the stuff. Never!