What is true happiness?

Catherine was married off through a political arrangement from an earl's house to a higher-ranking duke's house, where she was treated coldly by her husband, in-laws, and even the servants as unworthy of being the next duchess. However, that's just how political marriages are—it can't be helped. She lived thinking that if she just endured it, things would work out, but her heart was already in tatters. Then one night, she woke up, went to the bathroom, and when she opened the door, she found herself in an unfamiliar place. This is an original otherworld story with a relaxed tone. It's convenient storytelling. I'd be happy if you could overlook that.