The last Valois king of France desired to marry the lady, even going so far as to want to initiate divorce proceedings to dissolve her marriage to the Huguenot prince de Condé. However, Marie died (either of puerperal fever or of a lung infection according to her wiki) before much of anything could be done.
WI: Marie survives and Henri manages to get her divorced and marries her himself? Can Condé's 'falling away' from the Catholic Church mean that their marriage is no longer recognized as valid? And what might be the results of her marriage (both the dissolution of her first and the contraction of her second)?