Some dogs that come from an abused background never fully trust humans again so I really do commend you for giving this girl the chance at a life again.
Now I think there are some things that you can do that might help the situation. You might use a trap but that might cause set backs in her trust of you. I would ask your vet for a sedative that you could use in her food to sedate her. At that point, I'd get a harness on her and get her vaccinated again. I'd also get a leash on her and leave it on her. I would let her trail it around the house and keep her in the house. You can use the leash to take her out to eliminate.. She will get used to having the leash on. This will help her get used to the leash and allow you better control of her. About the longest I've seen a dog not move because of a leash being on was about 6 hours at which point they moved in order to be fed.
Once you have her contained in the house with you and not free roaming, she will likely adjust to your presence easier and be more dependent on you for her food and outside time. Once she realizes that she needs you for those things, she will likely start being more approachable. Of course, this is assuming that you want her in the house. If you don't want her in the house, it will be more difficult to get her used to you. In the house, she would be around you all the time and realize that you are not going to hurt her. Outside she would only have limited contact with you even if you contained her. Right now since she free roams, she likely feeds from various places and even catches food as well.
As I mentioned, some dogs never recover and it is something that we just have to accept. In your dog's case, she might not reach the point where she wants you to pet her or be with you but at least you have provided her steady meals and a place she can come to.
As for vaccinations, you can have a vet come to you and vaccinate her. If you can get a sedative, then you can crate her and the mobile vet could vaccinate her through the crate if it is a wire style crate. Most areas have mobile vets now and you can try and locate one on the site below. Just put the information in the house call vet area.
If you are in a rural area, ask your neighbors with livestock what vet they use as most vets treating livestock make house calls and will likely not mind vaccinating your dog once you explain the situation. However, if your vet will agree to a sedative, then you could just take her in after she is sedated and release her once you are back home. However, if you really want to try and domesticate her, you should try and get her into the house for an extended period of time so she depends on you and learns to trust being around you.
It basically depends on whether you want to be closer to her in which case, bring her inside and if you don't mind her being an outside dog, sedate her, have her vaccinated and continue to acclimate her to your presence when she decides to come around when you are outside. There really isn't any quick easy way to get her to trust you that your are not already doing in the present circumstances.
If you need clarification or I haven't been clear enough, please reply so I can continue the discussion. I hope this information is helpful to you and you are satisfied with my response.