For the wedding of her older brother, Prince Felix to the German born Claire Lademacher, Princess Alexandra wore a blue Tadashi Shoji gown. Alexandra wore pearl earrings and had her brunette hair in an updo. She also served as a bridesmaid. 

The religious ceremony took place on September 21, 2013, at the Basilica of Sainte Marie-Madeleine in Saint-Maximin-la-Sainte-Baume, France. They were first married in a civil ceremony in Königstein I'm Taunus, Germany, on 17 September. It is tradition to hold the civil service in the hometown of the bride. 

During the ceremony, members of the wedding party read "Lord Hear Our Prayer" in different languages including German, Luxembourgish, English and Spanish. Princess Alexandra read the Spanish portion. It is said she is conversational in the language; this does not come as a surprise as her mother, Grand Duchess Maria Teresa is Cuban.