Zoey = survivor_teenangst
The only parts of the original model that remain are the face, hands, holster, and belt buckle (which is re-textured). She has all facial expressions and her speech animates.
Install by double clicking, or placing in ...\left 4 dead 2\left4dead2\addons. Have L4D2 Add-on support installed: Steam->Library->Tools->Left 4 Dead 2 Add-on Support.
Update 6/26: -Zoey in The Passing's finale no longer does a dance that collapses the game's universe. She always stands with her arms folded. -Hair specular intensity reduced. -Leggings are now gray and black instead of white and black. -If you still see something strange about The Passing Zoey, post a comment. I'm aware the Passing intro Zoey isn't changed from her default look, I may look into fixing this in the future.
Update 6/28: -Zoey's hair now moves around when she does (jigglebone). -Zoey's hair texture improved. -Zoey's pistols appear in her holster when not being used. -Zoey's melee weapons appear on her back when not being used. -Now includes L4D-on-L4D2-style add-on onto Rochelle, since their models share the same rig (besides jigglebones) and animations.
Update: 8/23 - 1.3 -Fixed wonky thumb anatomy viewmodel. -No more Zochelle version (increase file size unnecessarilly, never included proper voice/name swap (impossible without COPYING THOUSANDS of WAV files), no more extra compiling the same model twice and double VPK madness).
Update: 8/23 - 1.3a -Fixed thumb even more -Fixed a sound issue, Zoey's voice and gunfire volume is normal
Update 9/16 - 1.4 -Updated for original animations -1.4a - fixed hair jiggle