One of the best -- if not the best -- of the early 1970s, Hammer films, this is easily Pitt's finest movie.
She plays Countess Elisabeth Nadasdy in the late 17th century, a real person that bathed in the blood of virgins thinking it would restore her beauty. Of course, in this film, the technique works. Pitt plays both a younger version of herself and an old, witch-like one.
The evil Countess even kidnaps her own daughter, so she can pose as her while she gallavants around as a young hottie.
Hammer got into T&A in the 1970s, and of those "adult" oriented horror films from the studio (which included "Vampire Lovers" (also with Pitt) and "Lust for a Vampire"), this is the best, although "Vampire Circus" is amazing as well.