One time, I went around getting rage for SS, but there was no animated around, literally. Everything was like gone, from people killing. And strangely enough, Landy showed up, and when I got there, she was full health, so I know it was a new spawn, not an old one. I don't think there is a sure fire way to get her to spawn, but the killing method seems to be the most effective/possible.
EDIT: I didn't realize this was a Necro of a 6-month old thread?