vogueing across the world, she was a 19-year-old dance student at the University of Michigan. For the first time, her ballet classmate and fling Peter Kentes, now 72, is sharing his story about his relationship with the “flirty” global icon — which even included a naked shower together.He is also revealing rarely-before-seen, intimate images and video of her from their college days — circa 1978 — as she currently battles a shocking health crisis that delayed her much-anticipated world tour.The photos are a far cry from the superstar image she built over her four-decade career, with her latest feat — a self-congratulatory tour nodding to her body of work, aptly called “Celebration” — disrupted by a bacterial infection and hospitalization last month.In pictures obtained by The Post, the pre-fame Madonna poses for Kentes’ camera in a red and yellow floral print dress with white crew socks and pink ballet flats.