This is anecdotal, but my husband had benign positional vertigo a few years ago, combined with another illness. When it first came on, there was no way he could work out. He did the crystal resetting procedure (Epley, you can google it) and it got better over a period of weeks. His doctor didn’t give him any exercise contraindications other than to change directions slowly, particularly getting up and down, and to return to exercise gradually. His body told him pretty quickly what felt tolerable.
Does your client have doctor’s clearance?