Susan Sullivan is the 3rd daughter of the Duke of Somerset. A twenty year old girl, finally
making her debut to the ton of London, her first time since her fathers death in 1809. Her, and her family going back to London was such an unexpected thing that had happened to her thinking they were going to spend there days in Somerset, but her, and her siblings must get married, except for the eldest, their sister, who is studying abroad, and a spinster, just like Abigail, the 2nd daughter. Susan spends most of her time with the Duke of Hastings, and Daphne Bridgerton, but when the prince of Prussia comes to London, Susan's ready to blossom like a rose.