When I have integrated cats, I usually take it more slowly than one day and then allowing the door to be opened. Sometimes, it has taken several weeks to months before my cats could be integrated, let alone if you have a dog.
What kind of dog do you have? Is the dog aggressive or hyper? That could scare the cats, especially C.C.
How old are these kitties? I read some of your other posts, and they seem they are at least several years old?
Have you been able to handle C.C.? Hold her or pet her? Is there a litter box in the same room? Plenty of food and water? If these were my cats, I would allow them some solitude for a few days, and not allow the dog near them, or vice versa. I had a beagle at one time with several of our cats, and one day all hell broke loose, when the dog caused a major cat fight. I had to give my poor dog to my daughter, as there was just no way that they were going to integrate peacefully.
Has C.C. not eaten anything? If she hasn't, you may have to try to offer baby food (no onion), even tuna people food, or small bits of chicken. If you have some Hill's A/D canned, you could mix some water into that and place it in a small bowl or on a plate, and put it near her. Make sure to warm up some food, to make it more palatable. Can you check her scruff to lift and see if it springs back? Hopefully she is not getting dehydrated, as you may have to take her to the vet's for fluids, because you can't let her go without eating or drinking.
Could she be constipated? Has she been looked at by a vet recently? I guess I would be very worried also, when a cat has shown no signs of eating or drinking or using the litter box.
Does she do well with her brother, Finn? They get along well, is what I mean?
Keep us posted, but worse case scenario, I would have her looked at if she is truly lethargic and absolutely not eating or drinking. She could go into hepatic lipidosis, and that is something not easy to deal with.
I am not a vet nor vet tech, but have had a lot of experience with stray and feral cats. My cats are all indoors once I adopted them.
Jean and Charcoal (GA)