I just sent this to Six Sentences. Let's see if they bite.
"The Kindness of Strangers"
She had never made the wish aloud, which is the lesser part of why she was shocked to wake up one ordinary morning and find that two hundred pounds of protective, insulating fat was simply gone from her body, and, far from being saggy and old-looking, she was fit and strong and beautiful for the first time in her twenty-eight years.
Initially terrified by the unfamiliar state she now found herself in, then sedated by an overwhelming cascade of neurotransmitters released by an inhumanly instantaneously evolving spiral of DNA, she huddled under a sweltering pile of blankets in her bed until her mother knocked urgently on her bedroom door, then entered to assess the transformation.
Her mother surprised her further by, rather than betraying any disbelief, expressing a grim resignation and quietly saying, "It is your time."
It was convenient that she'd never established any social bonds and had a job she could unremarkably disappear from, because now her mother packed some money and a few other things for her into a small suitcase, put her on a ship to the other side of the world, and hugged her goodbye, saying through tears, "You must call me once."
When she did call her mother, it was to confide her dismay in finding that, in her new location and form, that the kindness of strangers was a relative thing, as she was taken aback by the gracious opening of doors and other everyday courtesies from strangers, the kind of people who scorned or ignored her in her previous incarnation, and she felt alienated and apart from humans in a whole new way.
Her mother's vocalizations through the telephone triggered yet another immediate evolution in her DNA, her muscles instantly building mass visibly under her clothes, and her jaw setting with resolute predatory purpose as the instructions came across the telephone line, the most important of which was "Be sure you cull the right ones."
Edit: Just heard back - they're going to publish it on the 25th. Yay!