I think at such shallow angles it's the plastic surface that becomes reflective, not the metal layer with the pits and grooves. Hence the lack of diffraction (and hence why it works with my black PSX disc).
She's using a CD-RW with blue/purple dye. The reflection is definitely coming off the surface.
Everything reflects light, but not everything reflects it clear enough to read documents through. I haven't held a CD in ages, so it it's possible that folks don't remember exactly how reflective they are. ¯\_(ツ)_/¯
Almost everything reflects light. The discussion is on why it can be used as a mirror.