October 1537, in Monzón, the Emperor wrote to her: Mary served as regent of the Netherlands so well that Charles forced her to retain the post and granted her more powers than their aunt had enjoyed. Unlike her aunt, Mary was deeply unhappy during her tenure as governor and never enjoyed her role. In May 1531, having governed for only four months, Mary told her brother Ferdinand the experience was like having a rope around her neck. While Margaret had been considered truly feminine, flexible, adaptable, humorous and charming, Mary was unyielding and authoritarian. Margaret accomplished her goals using a smile, a joke, or a word of praise, but Mary used cynical and biting comments. Unlike her aunt, Mary was unable to forgive or forget. She recognized this lack of "power as a woman" as her main problem. Guardianship over nieces Assuming the regency in the Netherlands meant assuming the guardianship of her nieces, Dorothea and Christina of Denmark, the daughters of her older sister, Queen Isabella of Denmark, who had died in 1526. Upon Isabella's death, the princesses had been cared for by Archduchess Margaret. Charles now relied upon Mary to arrange marriages for them, especially for Dorothea, whom he wanted to place on the Danish throne. In 1532, Francesco II Sforza, Duke of Milan, proposed a marriage with Christina, who was then 11 years old. Charles agreed to the marriage and allowed its immediate consummation. Mary determinedly opposed this decision, explaining to Charles that Christina was too young for consummation of the marriage. Charles ignored her, but she nevertheless managed to delay the marriage. She first told the Milanese envoy that her niece was ill and then took her to another part of the Netherlands for "serious affairs". Christina was finally married on 28 September 1532, but Mary managed to postpone her departure until 11 March 1533. Immediately after Christina's departure, Mary fell ill and requested that she be allowed to resign as governor, but Charles did not allow it. A year later, Dorothea too was married. A few months after Dorothea's departure, the now widowed Christina returned to her aunt's court. King Henry VIII of England immediately proposed marriage to Christina, and Charles urged Mary to negotiate the marriage. She was not in favour of the union, and delayed. Henry VIII was excommunicated in 1539, at which point Charles had to end the negotiations. Relationship with Charles