So here's the update. I gave her a few more days, and while she improved slightly she was still pulling feathers out of one of the EE's, and still laying thin-shelled eggs which she would promptly eat, and so her "unhappy day" came over the weekend. The 2 EE's seem to be calmer, although I do think they realize she's gone and they seem a little unsure of things right now. But at least they're not being bullied, and I hope that they will forget about eating eggs now that the main culprit is gone (they're not laying right now - it will probably be a couple of months at least before they start again). Fingers crossed that we will have a more peaceable kingdom, and in the spring I'll get them some new sisters (but I think I'll stick to EE's from now on - they seem the nicest . . . )
Many thanks to all of you who responded, mostly for being nice and understanding. It was a difficult step to take, I did not take it lightly, and I appreciate that I was not slammed for it.
Cheers to all, and happy holidays!