Well... My guess is 1. She "might" be a wolf, a dragon's mortal enemy (they don't have a definitive proof yet) so bringing them is a pretty big risk; 2. Even if she is not a wolf and they took her, imagine if a king of a kingdom went out to look for a missing family member but came back with a women and a child, especially with the said family member being so close to said woman. The rumor mill will have a lot of gossip and scheme to churn out; 3. They are kind enough not to harm them just to bring Ruby back, so i figure dragon people don't want to do anything that went against the wolf's will or anything that would harm them like point 2; and 4. A country won't go anywhere and if there is a trusted and competent subordinate, the country could and should run for a while without it's ruler just like if there is a war where the ruler need to be in the battle field or when there is an expedition so they feel that there is no need to rush yet.