Get a liquid test kit asap. The API freshwater master kit is a good one and easy to find. you should be testing your water several times a week, especially at the beginning until your tank is cycled. shrimp is not really an appropriate food for her. Earthworms, either red wigglers or european nightcralwers, are best. Since you are in the US, i suggest ordering from uncle Jim's worm farm. Red wigglers will probably be the best size for her now, but eventually european nightcrawlers will be the better (they're just very big). You can also supplement with repashy grub pie and soft sinking pellets.
Her gills are definitely in poor shape on that side. I'm suspect of maybe a fungal issue though I cant see anything obvious in the photos. Tea baths are a simple, effective way to treat many different minor ailments. Black tea contains tannins that provide natural antibacterial and antifungal properties. It can also help soothe abrasions or minor injuries. Just brew one bag of plain black tea in a cup of boiling water for about 5 mins. I use tazo english breakfast tea, but any plain black tea will work. Just make sure there are no spices in the ingredients. after brewing, dilute the tea in cold water until it is a light amber color. She can stay in that overnight with no problem, or just several hours during the day. repeat daily or every other day (with a new tea solution) for 3-4 treatments and see if she improves at all.