Sheva Voice for Rochelle

1) - Locate the game directory: Steam\steamapps\common\Left 4 Dead 2\left4dead2\sound\player\survivor\voice

2) - Before extracting, I recommend creating a new backup folder and placing the original producer/Rochelle lines in there. 

3) - After removing/backing up the original producer folder/sound files, extract the new producer folder (Sheva's lines) into Steam\steamapps\common\Left 4 Dead 2\left4dead2\sound\player\survivor\voice 

OR   

extract all the audio .wav files into a new folder named producer within the same directory (i.e. Steam\steamapps\common\Left 4 Dead 2\left4dead2\sound\player\survivor\voice\producer).

4) - Load up Left 4 Dead 2 and type snd_updateaudiocache into console and restart the game. If that doesn't work, try snd_rebuildaudiocache (this command takes much longer) and restart the game.

Have fun!

If you want to disable this voice mod, you will have to remove the new producer folder (Sheva's lines) and replace it with the original producer folder (Rochelle's lines). 

OR

If you verify integrity of game files through Steam, it will retrieve the original voice files too (though it may remove other  mods). The next time you load Left 4 Dead 2 you will have to type in snd_updateaudiocache OR snd_rebuildaudiocache and restart.

This mod is also on the workshop, but the installation instructions are slightly different. At the end of the day, you just want to place the producer folder into the same directory (Steam\steamapps\common\Left 4 Dead 2\left4dead2\sound\player\survivor\voice) and update the sound cache (snd_updateaudiocache or snd_rebuildaudiocache) for it to work properly.