You can try pre made raw. Its soft enough for her to chew and the ingredients are great. You have done what lots of people wouldn't have...adopted a senior dog that on top of that has clearly been somewhat abused....God Bless YOU!!! See what the vet says about her health, at the very least she can live out the rest of her time in a warm house, with good food, and people that love her. As far as potty training, mine was 12 weeks and outside for about a month and I had a heck of a time. Its all about routine and being consistent. I'm sure yours can hold it longer then a puppy. Good Luck and please keep us updated.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD