I found this excellent review/analysis on Kenneth Muir's blog a few months ago. Easily the most insightful review on the Net:
Muir talks about the resurrection theme in detail. Joker and Batman are both terrifying spectres who haunt Gotham City; she created them, and they are her children in every sense.
I like that idea a lot. It fits perfectly with both the visual motifs and psychological underpinnings of their respective alter-egos. And in a pinch Catwoman/Selina fits with the resurrection theme as well.