I have had clients with vertigo, and went through a bout of it myself. It can be moderate to severe and can change from workout to workout. First, make sure you have asked her if she knows or is investigating the cause? How long has she had it? What makes it worse? Better? That's a good starting point. And then work with her day by day. Take more time with transitions, give her time after making a major positional shift to let her system 'reset'. Try to reduce the numbers of positional shifts in the work for her - which may mean using some common sense and adjusting variations and transitions. Make sure she knows if she is having a bad day, not to drive - and not to worry about missing her session if she needs to. The good news is, depending on the cause, Pilates can help her improve. good luck, zoey