Well, I love Kara, and everyone loves Barbara. And Barbara manages to involve herself everywhere, which means that Supergirl/Oracle is easy to set up. So it seemed like a natural choice, especially because I don't read much DCU and don't have a long list of characters that I'm able to read/write. But in any case, I desperately wanted to read some Supergirl/Oracle and when I couldn't find any decided I would have to write it myself.

I think I have read "Divide and Conquer" before. It's a good fic and well-written, but my main thought is to remember seeing the idea that Amy was manipulated by the First elsewhere, and to wonder how that piece of fanon became so ubiquitous.