The Sisterhood by Sheldon Lord

'Women without men in a forbidden variation of the game of love' Published at last! That much -discussed novel about 'the third sex' that has invaded the world of fashion ...

From the back:

Styles by Stella (for women only)
Three men had played violent episodes in the career of Stella Morgan, and then had been cast aside. For the path to the top of the high-fashion art world was 'for women only'. Particularly, it was the happy Lesbos hunting ground of Countess Helen Litov -
Helen's money made the 'Sisterhood' powerful in its campaign to infiltrate men's professions.
Helen's husband brought in the business... and was also the bait for new women... whom she initiated after the Count was finished with them.
Helen's favorite was Stella Morgan. But as the Counte meant to keep Stella for himself, it meant a final showdown in this strange triangle.
As for Stella, her ambition was as ravenous as Helen's desire - and so she had come at last to the crossroads....