It was so hard to say goodbye to Irene's family, but she knew that there was nothing more she could do. Her mother was in mourning and she wanted to do so by herself. Her brother was seen very little as he found monsters to fight and dedicated himself to his sword further in his father's memory.
When she approached Henry about leaving, she could see his relief, though he refused to force her hand one way or another. It was she who had to make the decision.
They had been loving one another so thoroughly before her father's passing, it must have been hard for him to suddenly accept her lack of affection. She was ready to get back to the Duke's Tower and be husband and wife on their own terms. It would be good for both of them to begin their life together.
She also missed the apprentices and wielding her sword. Practicing herself to the very limit of her stamina was cathartic in its own way.