The Spermulites, shapeless inhabitants of a dying planet, decide that the only way to save their planet is by conquering that disgustingly carnal planet Earth. To do so they transform themselves into the bodies of attractive women - except for Werner (Udo Kier), who is accidentally transformed into a hermaphrodite - and attempt to suck the life out of all the men on Earth (kind of like horny vampires)!
In 1977 a german magazine featured an article, ranting in indignation about Irina Ionesco letting her then 11 year old daughter, Eva Ionesco, appear in this 'adult' film, and appearing naked at that (though evidently not in any sex scenes). This article included still shots of Eva from the set, both dressed and fully nude, as well as alongside other women who do appear in the film, so clearly she was attached to the project at one point or another.
However, there are currently 3 different versions of this film floating around the net nowdays, none of which has _any_ scenes with Eva Ionesco, nor does any of them include her name in the credits.
So it is highly plausible that all of her scenes were never intended to actually be included in the final version of the film, and that the whole thing could just as well have been a publicity stunt (one of quite a few) orchestrated by her mother.