I rescued a 2 year old cat from a shelter three weeks ago. I took her because she was so afraid of everyone I was sure nobody else would take her. About two hours after I brought her home she was playing, eating and just generally being happy. I kept her alone in a room for about a week because I have another 9 year old cat who had never met another cat since being a kitten. When I let them get together the new cat LOVED him. He tolerated her and now seems to like her.

Everything was great. She was very playful. I have a few toys that she loved. She would play with each for 15 or 20 minutes on her own. She would run around and just be active and happy.

Three days ago my neighbor came in with her little dog. I did it because I have a very dear friend who needs surgery. She has a toy poodle and she will need me to take care of him while she's in the hospital and rehab. My neighbor's dog is the same size with the same temperament. Also, she's been in my house with my other cat many times.
The new cat was terrified. She ran into the furniture and wall and finally up the stairs where she hid. The dog went home after 15 minutes. The cat didn't eat for an entire day. She didn't come downstairs for two days. It's now three days and she won't play with anything. She's eating and walking around the house, but she's a different cat.
Is there anything I should do, other than give her affection and time? I feel awful, but this friend of mine has done more for me than I could ever repay her for. If she needs me to care for the dog and I have to keep the cat upstairs for two weeks then so be it.

She also started something new today. The litter box has a cover on it. All of a sudden she started scratching at the box and the cover, from inside. She did it on and off for about an hour. I took the cover off and she seems OK.
I know that this poor little thing has been traumatized and I want to do what I can to get my happy kitty back.
Any suggestions would be appreciated.
Just try to treat her normally and let her do her thing. Of course monitor her eating, drinking and litter box habits because stress can cause health problems. Most of all, don't baby her or act all "poor kitty" because they pick up on that.
I rescued a 2 year old cat from a shelter three weeks ago. I took her because she was so ... traumatized and I want to do what I can to get my happy kitty back. Any suggestions would be appreciated.

Time heals all wounds..Expose her to the dog more often, and pretty soon she will get used to him/her. My 5 cats all came from different backgrounds, and exhibited different behavior to each other, and to other people and situations, but now they are all pretty much acclimated to our home and what's in it and the neighborhood. Even Sarah, our latest, who hated all the other cats and alienated them all, is now tolerant of all of them and can exist in the same room with all of them. (It took her almost two years) Your new cat was probably traumatized by a dog in the past, but she will forget that and learn to get along with the dog in time.
Just try to treat her normally and let her do her thing. Of course monitor her eating, drinking and litter box habits because stress can cause health problems. Most of all, don't baby her or act all "poor kitty" because they pick up on that.

Oh, boy, don't they. Cats are drama queens!
Like others have said, it might take some time for her to re-adjust. Keep all routines (feeding, etc.) the same, as cats crave routine. Play with her; it's great bonding time for both of you.