An idea I thought of was having Chelsea react to a person who's only partially immune to her - not by way of any protection powers or something like what Elspeth has, but something like a character who sees and talks to ghosts. If this incarnation Chelsea can't affect relationships with dead people - this could become an interesting RP with people that everyone mysteriously stopped caring about, then died with equal mysteriousness. Except for the one person that can tell what's going on, but only after it's been done. It's a bit dark, but it could be interesting to see.
I like just about any initial reaction stuff, especially with normally confident characters thrown out of their element - so summoning to Elcenia's a cool idea. Milliways is always an option, though that could easily become a bit stale if used incorrectly.
On a separate note, I'll answer the call to sandboxing. I couldn't due to a mix of workload and shyness earlier, but since I've finished my large-scale project last night and no one else answered, it seems like the kind of thing to do. How would you like to be contacted? I've got a few Dreamwidth accounts, along with a Tvtropes account, this account, and of course gmail. I'm not sure what you'd prefer - I'm not very picky.