It’s awesome that you are helping this client to get exercised and stay fit! Without knowing much about her limitations and/or condition, I would think that any upper body exercises shouldn’t be a problem for her. She should be able to do most of the exercises that require sitting and maybe some while standing but might require your assistance. TRX could be one piece of equipment that she could also use as long as you are there to assist. Another option would be to do some exercises while using a wheelchair. By adding some extra weight on it, so she can push it around to increase her upper body strength and endurance (or even uphill). Also while on a sitting position, she could incorporate some battling rope training as part of her exercises (just make sure you have secured the wheelchair or any other chair she is using). She can also use tubing for upper body training and depending on your assessment she should be able to perform many of these exercises with little or no assistance at all.
Swimming is another type of training she could also try (if she knows how to swim). I could provide you with more options, but without assessing her it would be difficult to do so.
I hope this helps.