VEVO has relationships with record labels... not the individual artist. Mariah herself does not have control on the content of her VEVO channel - the record companies do.
The Glitter videos will never be on VEVO because they are not owned by a record label.
Your first paragraph is correct, however the Glitter videos are owned by Virgin Records which still exists after a merger with Mercury Records, and owned by Universal. However it really is of no interest to Universal/Virgin to upload videos from a flop album by an artist that is not even on their roster.