Most foxes on the island of Viridis would consider working for rabbits to be rather beneath them. Once upon a time, Deirdre was one of them. However, ever since she moved to the rabbit-controlled city of Oseille, under the excuse that she wanted to keep an eye on her daughter, she has come to respect and even admire her new friends. Her blooming relationship with a certain sweet rabbit doe has certainly helped change her mind, too. So much so, that she has come to regard living in Oseille as a mark of honor.
So much so that she has decided that the least she can do to thank them for their trust and their generosity is to help boost their defenses. It gives her something to do, keeps her (mostly) out of trouble, and at this point in her life the rabbits are probably the only ones who like her enough to employ her anyway. In return, Oseille gets the best General and tactician Viridis has seen in a dozen generations, and banditry and theft have all but vanished from the region.
Best of all, Ciara gets to see her mother more than once a decade.