Not to psychoanalyze too much, but it seems to me that the foot fetishist idealizes a dominant woman who likes to have a man under her heel looking up. The ass fetishist seems to desire a powerful, but not necessarily dominant woman, in order to look up at her strong legs and globular buttocks as she strides across the world like a Colossus, walking away.
The main character of Monella (Frivolous Lola in the Anglo world) is indeed powerful, and powerfully sexual, but she's stuck in a provincial 1950s Italian town that seems compelled to stick her in the Black Iron Prison of married monogamy to a dull sap, while she just wants to get rid of her virginity a.s.a.p. Said beau is full of patriarchal claptrap about sacred love, so the film becomes an inversion of puerile American sex comedies- here it's the young girl who just wants to get laid.
Brass seems to recognize the sexual superiority of the female, and to be arguing that no woman need settle down with one man, the cock being inferior to theclit after all. So, for an "erotic film", it's got a surprisingly feminist slant, and some decent dance sequences!