TRX might be a little too advanced for a person of that age, especially if she is getting dizzy and you’re not sure why.
I love getting a patient’s history, FIRST. What is her typical day like? When was the last time she was in an exercise program? When was last time she seen a doctor? Resting HR? Resting BP? What is her medical/orthopedic history? etc etc. This helps me better manage the program and I can have an idea of what to expect or possible complications when training them.
Also, she may be suffering from a condition simply called hypoglycemia. Is she eating before her workouts? If so, what, how much and how soon prior to exercising does she eat? Could be dehydration or a number of things. But that is where the medical history helps.
I also agree that it may warrant a visit to her doctor, unless the visit was recent. It may simply be that the workout is too intense for her and scaling back the intensity for what is right for her.