Goddess Djerdlid wanted to test her new slave. She had to see how obedient he was and what his limits and boundaries were so that she could push and stretch them to their limits. She chose to use her dirty soles to do it. She asked him to lick her soles and he did it. He was scared of her so he did what she asked and she liked that.
Goddess Djerdlid had nothing to do with her ex. She had already moved on but he had not and he kept bothering her. She had resisted meeting him but when he became too much, she had no choice but to do it. She did it not for him but for her to have fun at his expense as she had him lick her boots and her soles until he realized she was using him.
Goddess Djerdlid wanted to express herself but she did not know how to do it because she was fed up with her slave and she wanted to make sure that by the time she was done doing it, he would never mess with her again. He had to lick her feet and especially her dirty soles before she felt that it was enough and she let him go. He did it.