I think it is important to note that i will be working closely with her surgeon and physio, but i would like to do some research regarding exercises and have a really clear understanding of current thinking in terms of getting her back to some level of fitness as she has put on over 20kg since surgery.
I would first start with consulting their surgeon and physician, it is a very important to be sure that whatever you decide to work with is safe. I have created a program where all exercise is done sitting down, however as with all health programs consult a physician prior. We have been Kaiser Permanente approved so maybe this would be something to start with. We have a Chair Yoga program that you can look over and see what could work best. I wish your client the best of health and hope you can find something to keep them in good health!!! http://www.chairdancing.com/stretching-flexibility-relaxation/
I think you can understand why most trainers would be hesitant to offer specific answers. Without oneself working with the client and the medical practitioner it is difficult to make specific recommendations, and it is possible to overstep one’s scope of practice.
I will say that I have worked with many people with a variety of such spinal conditions, and I would encourage you to do some research on the uses of yoga. You don’t want to start teaching yoga if you aren’t trained in that modality (I cannot tell from your post), but you might find that some of the stabalization and spine centered work would give you some good ideas of places to focus.
May I suggest you look at teh work of Judith Lasater? She is a Physical Therapist as well as a very senior yoga teacher. I often recommend her book ‘Yogabody’.