The regular Windows installer for the
official Liquid Rescale Gimp 2.8 plugin defaults to the Gimp 2 folder not the [User].gimp-2.8 folder.
The following files are installed.
C:\Program Files\GIMP 2\lib\gimp\2.0\plug-ins
gimp-lqr-plugin.exe
liblqr-1-0.dll
plug_in_lqr_iter.exe
C:\Program Files\GIMP 2\share\gimp\2.0\scripts
batch-gimp-lqr.scm
C:\Program Files\GIMP 2\share\
gimp-lqr-plugin (folder)
I'm not totally clear on which files you've already installed or your Gimp setup, so use this info as a guideline.
Do check for duplicate files between Gimp 2 and .gimp-2.8 folders.
I hope this helps sorting it out.