It can be much harder to figure out the "right" way to train the ones that were abused. Mario was abused too, but good news for you and us, is he is about 95% recovered. Now, no one but me would know now that he had been abused. I have not seen signs in some time, but today I came in the house carrying a longboard for a project and he got all hang dog and cowered. Soooo, we had to work that out. We just work through every issue as they present themselves.
For the leash issue, yeah try hooking one on her for short periods of time outside (if you have an enclosed area) over several weeks to months and see if she will adapt to walking around with it. If she will then try showing her a treat, stepping a tiny bit forward and tapping your leg with the treat. See if you can inch her along with treats, gentle, soothing praise and lots of love.
She may be afraid you are going to load her up and dump her or something. Love and patience can work miracles on these furry kids
