You can go to dogfoodanaylsis.com to find a good dry food. As said, Old Roy is not the best. I would also not feed her seasoned meat from Taco Bell. You know you made a mistake by hitting her and know not to do that again which is good. The only thing I want to say about that is please, please be careful drinking around her. They are so little and accidents can happen so quickly.
My only other advice is to give her lots of love and she will love you back. Sometimes it just takes time but in the end, you are her whole world. You'll get tons of advice on food- I used to feed Merrick dry but there are a lot of other great foods. It's great that you are making sure she is getting enough water and I'm sure someone will come along to help you with the shaking. Good luck with her. I think it's great that you care enough to come to YT for help.
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"If you have men who will exclude any of God’s creatures from the shelter of compassion and pity, you will have men who will deal likewise with their fellow men." — St. Francis of Assisi, 1181-1226