The Serpent in the Garden — Jordan Castillo Price

Shirina has been studying an arcane scroll scrawled with tinctures and potions, and she's well on her way to becoming a master poisoner. Too bad her brother Dharmesh won't accompany her to the marketplace so she can obtain the final ingredients. He says there's a rapist prowling the village, and he won't tempt fate by parading his young unmarried sister around town. So he goes himself -- and leaves her behind. Alone. At the mercy of anyone who just might happen to drop by. (Erotica - short story)