Stephanie 4 is a morph (and some partial scaling) of Victoria 4.  You have to have the V4 base (not the version included with DAZ Studio) and install S4 to the same folder that V4 is in.  You can point the installers to any folder you want if you choose the DAZ Studio install option.  The options are poorly named as the Poser option makes the installer search for a/any folder/s with a Poser.exe file in it.