One day, when they met at his sister's house, being a little separated from he rest, the Duc was tempted to speak to her, but she interrupted him sharply saying angrily "I do not understand how, on the basis of a weakness which one had at the age of thirteen, you have the audacity to make amorous proposals to a person like me, particularly when, in the view of the whole Court, you are interested in someone else." The Duc who was intelligent as well as being much in love, understood the emotion which underlay the Princess's words. He answered her most respectfully, "I confess, Madame, that it was wrong of me not to reject the possible honour of becoming the King's brother-in-law, rather than allow you to suspect for a moment that I could desire any heart but yours; but if you will be patient enough to hear me I am sure I can fully justify my behaviour." The Princess made no reply, but she did not go away and the Duc, seeing that she was prepared to listen to him, told her that although he had made no effort to attract the attention of Madame, she had nevertheless honoured him with her interest: as he was not enamoured of her he had responded very coolly to this honour until she gave him to believe that she might marry him. The realisation of the grandeur to which such a marriage would raise him had obliged him to take a little more trouble. This situation had aroused the suspicions of the King and the Duc d'Anjou, but the opposition of neither of then would have any effect on his course of action, however if this displeased her he would abandon all such notions and never think of them again.
This sacrifice which the Duc was prepared to make caused the Princess to forget all the anger she had shown. She changed the subject and began to speak of the indiscretion displayed by Madame in making the first advances and of the considerable advantages which he would gain if he married her. In the end, without saying anything kind to the Duc de Guise, she made him recall a thousand things he had found so pleasing in Mlle. de Mezieres. Although they had not had private conversation for a long time, they found themselves attuned to one another, and their thoughts went along a track which they both had travelled in the past. At the end of this agreeable meeting the Duc was left in a state of considerable happiness, and the Princess was not a little moved to think that he truly loved her. However, in the privacy of her room she became ashamed of the ease with which she had accepted the Duc's excuses and reflected on the trouble into which she might be plunged if she engaged in something she had always regarded with distaste and on the frightening misery which a jealous husband might inflict on her. These thoughts made her adopt new resolves, but they disappeared the next day on the sight of the Duc de Guise.
The new alliance between their families gave the Duc many opportunities to speak to her. He gave her an exact account of all that passed between Madame and himself. He had difficulty in allaying the jealousy to which the beauty of Madame gave rise and any number of promises failed to reassure her. This jealousy enabled the Princess to defend the remains of her heart against the advances of the Duc, who already had won the greater part of it.
The marriage of the King to the daughter of the Emperor Maximilian filled the Court with fetes and celebrations. The King put on a ballet in which Madame and all the princesses were to dance; among them only the Princess de Montpensier could rival Madame in beauty. The Duc d'Anjou and four others were to make an appearance as Moors; their costumes would all be identical, as was usual in this sort of performance. On the first occasion on which the ballet was presented, the Duc de Guise, before the dance began and before he had donned his mask, said a few words to the Princess as he went past her. She saw clearly that the Prince her husband had noticed this, which made her feel uneasy.
A little later, seeing the Duc d'Anjou in his mask and Moorish costume, who was coming to speak to her, she mistook him for the Duc de Guise and said to him "Do not have eyes for anyone but Madame this evening: I shall not be in the least jealous. I am ordering you. I am being watched. Do not come near me again." As soon as she had said this she moved away.
The Duc d'Anjou stood there thunderstruck. He saw that he had a successful rival: the reference to Madame made it obvious that this was the Duc de Guise, and left him in no doubt that his sister was to play second fiddle to the Princess de Montpensier.
Jealousy, frustration and rage joining to the dislike which he already had for the Duc roused him to a violent fury; and he would have given there and then some bloody mark of his temper had not that dissimulation which came naturally to him prevented him from attacking the Duc de Guise in the present circumstances.
He did not, however, refrain from the pleasure of disclosing his knowledge of this secret affair. He approached the Duc de Guise as they left the salon where they had been dancing and said to him "To presume to raise your eyes towards my sister, as well as stealing the affection of the woman I love is altogether too much. The presence of the King prevents me from taking any action just now, but remember that the loss of your life may be, one day, the least thing with which I shall punish your impertinence."The pride of the Duc de Guise was not accustomed to submit tamely to such threats, but he was unable to reply because at that moment the King called both of them to his side. He did not forget, however, and tried all his life to exact revenge.