His By Right by Linda Mooney
She thought they were saving her life. She was wrong. Instead, Meredith Powell was kidnapped, taken aboard an alien spacecraft, and forced to prostitute herself to paying humanoid customers. But she had hope. She would only have to serve for two years, and then she would be returned to Earth.
It was a life she had to learn and adjust to, until one paying customer took a special interest in her. A customer who had other plans for her, and none of them involved returning her to her home planet.