In J.L. Styan's Restoration Comedy in Performance (1986), there is a chapter devoted entirely to actresses and female roles on stage. While Styan has little in the way of statistical information on audience demographics, he does speak to the influences of the male gaze in Restoration theatre that was a result of its more private and courtly (i.e. gendered and classed) re-formation after the English Civil War. Gwynn is mentioned several times throughout. But, in an effort to actually provide an answer to your question, the professional theatre of the period--which is where Gywnn found herself--was almost entirely a work dedicated to the upper crust of English society. As such, it tended to reflect prevailing patriarchal sentiments emanating from the Royal Court and would speak to its intrigues. The audiences were almost exclusively powerful men of the court--though some women would have been in attendance from time to time. Aside from the courts, the patent theatres (there were 2 year-round, with the Theatre Royal Haymarket making up the third during the summer months) enjoyed more mixed-gender audiences. But even then, they were still mostly attended by men and their audiences were also largely from the upper crust of society. To sum up, for Nell Gywnn, she would have been performing for audiences that were predominantly comprised of men. [See also: The Cambridge Companion to the Actress, Maggie B. Gale and John Stokes, eds. (2007).]