Jesus Franco's "Diabolical Dr.Z" (original title "Miss Muerte") from 1965 is one of the most amazing movies connected with long-nail fetishism...and its acting it's worth the look as well.
The plot as it appears on imdb says it all: "Dr. Zimmer, a neurosurgeon disciple of Dr. Orlof, dies when trying to prove that the origin of good and evil is physiological. His daughter seeks to avenge her father by controlling the mind of a Black-Widow dancer with long fingernails."
Mabel Karr (as the daughter) is gorgeous, diabolical and has nicely looking nails.
Estella Blain (as the Black-Widow dancer with long fingernails) is simply stunning.