Stuff That Makes People Think I Have A Lot Of Time On My Hands
I think that's an old GW Dark Elf Witch. If its not part of the Witch unit, it might be off of the Cauldron of Blood.
I did some searching on both Coolminiornot and Stuff of Legends, and she's doesn't appear to be part of the previous Cauldrom witch group (nor the current one, obviously.) I was unable to find older Witch Elf models that she matches. The mystery remains!
I have the same one - i did a little research, this is a Ral Partha miniature of an elven blade mistress:) GW did not make such pretty miniatures back then;)