Do I need to install G4 in the same location as V4?
Or can I install her in her own file?
I ask because I read she was a variation on V4.
And what about her morphs and such?
Yes, you need to install G4 in the same location as V4: she's not an independant figure but a V4 morph.
The provided Girl4 cr2 just loads V4 with the G4 morph already applied.
I just did that now following your information.
Does the G4 Makeup Pack, G4 Puppetteer Presets, and G4 Power Loader go in that same V4 file?
Yes, all Gen 4 female aspects go with V4.