On the subject of Mathilde's engagement to Napoleon III: At the time, he was not emperor, or even thought of in that way. Mathilde was a very intelligent, high-minded person, and she thought him not very smart. Once, she said something to the effect of she would like to crack his head open to see what was inside. Also, I don't think there was enough money involved in the deal for her father to allow her to marry Napoleon III. Later, when he became emperor, she regretted her decision, and she became one of his chief backers, financially and otherwise.
On Demidoff: He was a brutal person who was known far and wide for his violent behavior and bad manners. But he had lots of cash and Mathilde's family needed lots of cash. He also collected Napoleonic memorabilia, and he added Mathilde to his collection. Mathilde's father sold Demidoff a diamond necklace that had belonged to Mathilde's own mother (Catherine of Wurttemburg), so that Demidoff could give it to Mathilde and Fifi's third wife could continue to wear it. Nicholas I once told Mathilde she could always count on him, after learning of Demidoff's abusive treatment of her. In fact, Nicholas I gave Mathilde asylum when she first left Demidoff, and granted her a decree of separation.
Mathilde is a very interesting character. There is a lot of information on her. She was almost brilliantly intellectual and artistic, as were many in her extended family, but she was also, IMO, cold and calculating. She grew up in a bad situation. She hated her father for his constant money grubbing and her mother was emotionally and physically distant, with practically no relationship at all with her daughter. Mathilde's uncle, the King of Wurttemburg, once told Catherine (Mathilde's mother), something to the effect of, "dress her better and show her some devotion." She was still being dressed as a girl when she was a young woman.
