Safe assumption, Grace calls Sheryl the 9th Fairy (or was it 8th, someone should check for me ), which certainly sounds to me like there were previous test subjects. And blood keeps being brought up when we know that's exactly the kind of experimentation they've been doing. It tells us nothing.
At this point, if Kawamori goes back this late in the game and starts throwing plot twists and out of this world coincidences at us, it will ruin any sense of storytelling in this series. I guess this kinda thing works for the "Lost" crowd, but I think its just totally nonsense.
To me, Sheryl's story is far more compelling as the woman who was discarded not once but twice; the first time by her parents, and the second time by the people who used her in some very dangerous, and most likely illegal experimentation. She is left to die, but instead stands up and fights and in the end probably is a key to the Frontier's success.