I did the only thing I could think of. I emailed a third author friend and asked for a second prompt. So while I was writing Nicki's story in secret, I was writing Connie's story to show to Nicki. I'd finished Connie's story and was frantically working on the last scene of Nicki's when we went to a weekend get-together of author friends. I spent the entire weekend with her on the other end of the couch as I was trying to finish the story without her finding out.
I managed, with a bit of luck and her ankle bracelet to let me know when she was coming down the hall, and sent it in for the fic exchange. It was posted and I sent her off to look at my story, as if she hadn't read what she thought was my story a dozen times already. Instead she found Testament to Love.
I've expanded on the story since then, adding 5k over the previously published version (which itself was longer than the fic exchange story), and it will be published as a novella in June or July. Needless to say, I'm ecstatic. I only hope she loves this edition as much as she loved the first.