@FreeDuck,
Yep, I agree with JPB that this was a really tough age. I talked at the time about "satanic sixes," I was exaggerating of course but it was that six to early seven stage that was tough (hit different kids at different times in that window).
As in, I think that the recent issues could have more to do with a developmental stage than any specific catalyst (as in why she seemed "socialized" then but not now).
From my experience with this it really hit girls harder than boys -- sozlet had a bunch of Major Dramas with her friends around here, and got kind of annoyed with girls in general.
I wonder if Ducklet has been experiencing some early mean-girl stuff and instead of responding in kind, she's being more... direct?... with her own anger. That's pure speculation, just a hmm.
I know this must be terribly hard to deal with as a mom. I'm sure you guys will figure it out though...