Opposites attract. Star-crossed lovers, doomed from the start.
Her sense of justice to his sense of loyalty, illegal but loyal. She vowed to never court a rusher, her mother had made the mistake, with her life as the price. He was taught to never love, someone he couldn't trust. Love meant blind loyalty. He couldn't afford to make that mistake.
So they did the only logic thing. Guardswoman Cooper, the terrier and bloodhound, never courted, never loved The Piper, King of the Rouge. But in the dark of nights, behind locked doors Beka courted Rosto. Rosto fell in love with Beka. Both kept their promises to their memories. Beka never courted a rusher; Rosto was no rusher, not when they were alone together. Rosto never fell in love with someone he couldn't trust. Because unlike the bloodhound Beka would never give Rosto to the cage dogs. They loved each other and the bands they wore dangled from the chains on their necks. A bond so deep that not even their lives could interfere.
When they came for Rosto in the night she put her back to his. She refused to kill her fellow dogs, but she refused to give him in, so she fought. It was only when Goodwin tapped her baton to Beka/Cooper's that she fell. And as always he caught her before she had time to fall. Loyalties would be trusted, and Beka the Terrier's true justice came that night. Because he was a good man and she was not blinded by love, he did not kill the man they said he did. She gave up her life's work to defend him because he saved the lower city from many things, killers were the only ones he killed. She became his queen, though Aniki would always be the true queen. And she protected the same people with the same baton, from things she was blinded by before because that's her true lifes work. Justice.