I would make sure she is comfortable walking on slick/shinny/slippery floors. See if you can get her to experience a few elevator rides. I think the main thing is just socializing your pup to a lot of new places and novel experiences. Expose him to wheelchairs, gurneys, moving equipment inside large areas.
When I had my therapy dog tested, they checked for noise sensitivity, willingness to be handled by strangers, and his confidence in a new environment surrounded by strangers without me being there. Neutral to other dogs and other pets - at any one time a facility may have other therapy pets present, including cats and birds and rabbits, so my dog needed to not pay attention to those distractions.
One thing I found very helpful was teaching him silly tricks - made my visits start off on a good note, and a great way to break the ice and get people to laugh and relax around him.