In the Garden of Iden (1997)

Poor Mendoza. She's not thrilled about being sent to Renaissance England. It's a cold, backward, unsafe country. Gray curtains of rain. The food crawling with bacteria. No flush toilets. She won't get to see Shakespeare either. He hasn't been born yet. The English hate the Spanish like smallpox, especially now with bulldog-faced Mary on the throne. But Mendoza is no longer a frightened little girl in the dungeons of the Inquisition; she's a Company-trained botanist and has an assignment - to save Ilex tormentosum, a species of holly that will go extinct in a hundred years. She must save it for Dr. Z and the twenty-fourth century. Kage Baker, in her first novel, tells the story of a spunky young cyborg who, though an immortal operative, falls for Master Nicholas Harpole, a mortal with pale blue eyes, good legs, and a smooth, rich tenor that hangs on the air like a violin.