Marie of Hesse appears in James Pope-Hennessy's biography of Queen Mary as Mimi of Dessau, one of the many relatives that Princess Mary Adelaide kept bumping into on her visits to Germany. She was the mother of Adelheid of Nassau, the exotically named Bathildis-Amalgonda (Tilla) and Hilda (who remained unmarried). Mimi and her younger sister, Queen Louise, were nieces of the Duchess of Cambridge and regulars at the family gatherings at Rumpenheim. When The Tecks arrived in Florence Mimi, Tilla and Hilda were already in residence, which cheered up Mary Adelaide in her first days of exile.
I would like to know more about the Hesse-Kassels as they have several marital links to the Royal House of Denmark and are descended from George 11 of Great Britain (his daughter Princess Mary was grandmother to the Duchess of Cambridge).
If I remember correctly, Prince Albert objected to Queen Louise and her mother and sisters but I don't know why.