I sided with the witch about Hlormor Wine-Sot. It was a long battle and I ran away a good bit, but I kept losing fatigue. Eventually I beat him. Now I'm lost. I can't find Sosia again for my reward. Does she disappear after this battle? Is there a journal entry I can make and add in my reward? If she is still there where I left her I will keep looking till I find her. Otherwise I want to console the rest of the quest. Thanks for your help.

She will be at, or near, the spot where you met her. http://www.uesp.net/maps/mwmap/mwmap.shtml?centeron=Sosia+Caristiana

If you cannot find her there, you can use RA while standing near the place she's supposed to be. This will reset her location, in case she has wandered off.

I found her, Pluto! As it happens she was only a little further down the road from where I was. Thanks for your help! Now off to new adventures!

The Lord of the Underworld and his Ferryman having a discussion on the internet. Pretty damned cool.