Knowing that she couldn't have him didn't stop her from wanting him. If anything, it made it more intense. Now it wasn't a reality based option, it was purely fantasy, and instead of vague images that left her feeling aching and somewhat dirty in the morning when she recalled then, her dreams had turned very specific. Spock's head between her spread legs, the tiniest smirk on his lips as he nipped at her thigh. His tongue - his agile, nimble linguist's tongue - moving over her and learning her and knowing just exactly what she needed. Her nails digging furrows in his back, her legs wrapped around his waist as he moved inside her, his skin overly cool while she burned from the inside out.
Ridiculously specific, and in the morning she just felt hollow. But while it lasted...
Uhura whimpered in her sleep, thrashed her head from side to side and arched her back off the bed. It was agony, but for a few more hours, it was as close to the real thing as she'd ever get again.