But Stella was putting this idea forward in 1915

This is an interesting article The varied nature of women's sexuality: Unresolved issues and a theoretical approach: how can one not be predisposed towards a serious scientific piece on female sexuality which talks about 

the lack of consideration of the marked variability in the non-problematic sexuality of women

and continues

It will be difficult to establish a clinically useful conceptualization of women's sexual problems, and how they should best be treated, until we have a better understanding of the non-problematic variability of women's sexuality

It's a long piece with lots of reference to the literature on the subject and the various theories that have been advanced.

One pioneering piece of literature that is not cited, however, is Browne (1917) - Stella Browne's pamphlet (first given as a lecture to the British Society for the Study of Sex Psychology in 1915), The Sexual Variety and Variability of Women and Their Bearing Upon Social Re-construction.

The sexual emotion in women is not, taking it broadly, weaker than in men. But it has an enormously wider range of variation; and much greater diffusion, both in desire and pleasure, all through women's organisms....

The variability of the sexual emotion in women is absolutely basic and primary. It can never be expressed or satisfied by either patriarchal marriage or prostitution. It is found in the same woman as between different times, and in different individuals.