Any tips for dog amputees?

Hey all! My past client's dog had one of her legs amputated and we're getting ready for a longer stay in the coming months. When I sat her before, she was extremely sweet and well-mannered; however, she does have anxiety and does not like going outside when she is in an unfamiliar place. The owner had already discussed this with me and he is well aware of the situation. The dog loved me and I loved her, so when the time comes, she will be staying with me for a week (instead of a day). The owner told me that with a past sitter she literally did not go to the bathroom for 3 days! I am worried that this will happen during the longer stay and though we are working to have more day cares so that she gets more used to me, I was just wondering if you all had any tips for this!

You should know: she has trouble with her missing back leg and it is hard to get her up on the sofa (which her owner asked me to do), she is afraid of doors, not very willing to go out.