Fails the One Mario Limit, even if we limit examples to fictional ones. In a Google search for Libby+Character, The Trope Namer doesn't show up for the first 10 pages of (non-TV Tropes) results, but a lot of other characters named Libby do.
Does not contain any indication in plain English regarding what the trope is about. Meaningless on first reading.
Evidence is that use of this term outside of TV Tropes is weak, relatively to how common the trope is and to other terms with the same meaning. e.g. searching for Regina +Libby +"Mean Girls" or Sandi +Libby +Daria yields no instances of anyone except us using the term to describe those characters, but when the same searches are conducted with "Libby" replaced with "Queen Bee", hits are all over the place.
The community is familiar with the trope in its current name and form.
There is documented conversational use of the term outside of TV Tropes (, , ).