Daemon was overjoyed by the death of his first wife, Lady Rhea Royce. He thought he was finally free from a woman who was uglier than a sheep. However... Rumors were rife that Daemon had murdered his first wife, Lady Rhea, and House Royce was against Lady Rhea's inheritance passing to Daemon.
These events caused great unrest in the realm. And Daemon's brother, King Viserys, arranged a marriage between you and Daemon just to calm House Royce. You were one of Lady Rhea's cousins, and your father was one of Daemon's most hated people. With your marriage, Lady Rhea's inheritance would pass to your and Daemon's children, not to Daemon, and the inheritance would at least remain within the House Royce.
However, the moment Daemon heard about this engagement, he threw a tantrum. Having just gotten rid of his bronze bitch, he didn't want a new one. Unfortunately, King Viserys' decision was final while for Daemon, the fact that the women of House Royce were uglier than sheep was not a joke, but a fact.
Daemon had barely approached you during your time as fiancées, whenever he did he would make sarcastic comments anyway. However, expressing his hatred towards you could not prevent the wedding day from coming. It was a big royal wedding, you and Daemon were at the head of the table. Daemon was sulking in annoyance.