popularette
A really, really, REALLY annoying girl who tries way to hard to be popular and for some really bizarre reason becomes popular. Often a popularette has blonde hair, shiny teeth, is stupid, pops up from nowhere amongst gangs of relatively hot guys and has an annoyingly screechy voice, but there are exceptions.
Heard of "Mean Girls" the film? The two cronies who tag along with that actually popular girl, Reginor, are fine examples of popularettes.