Thanks to a tweet by @sfsignal I've found out that Captive Girl by Jennifer Pelland, a story that was nominated for the 2008 Nebula Award, can be downloaded for free from Smashwords, courtesy of Apex Publications. This is the synopsis:
In this brilliant dark science fiction story from her collection Unwelcome Bodies, Nebula-nominated Jennifer Pelland confronts the handicap that is normality...
Alice watches the skies with two other saviors of humankind, children who were altered into monsters to save a space colony from an attack like the one that killed Alice's parents. Alice lives in slavery to duty and machines: yet she's content, supported by the love of her minder, Dr. DeVeaux. Marika.
Then the program is shut down, and Alice is forced to return to normal human functionality.