In terms of real-world behavior, the mini-series version seemed more probable to me. Of course Sir Felix wouldn’t waste his time travelling down to the country to see Ruby, or take her out to the music hall in London, if she didn’t put out. And I wonder whether Trollope’s readers would have assumed the same.
Yet Trollope, perhaps for the sake of propriety, leaves Ruby undefiled. When push comes literally to shove in the novel, Ruby screams for help. She goes on to marry respectably. Her complacent fiancé asserts that she is a good girl. I think if she wasn't, she would have been fated to die by the end of the story, as is the fate of most fallen women in literature.
In Emma, Jane Austen references Goldsmith's short poem: "When lovely woman stoops to folly." I think Austen mentioned the "dying from shame" trope in a tongue-in-cheek manner. Recently, however, I’ve come across some examples of readers and critics arguing that there are some artfully hidden clues about sexual liaisons and love children in Jane Austen’s novels. If so, these are fallen women whose offences go undetected and unpunished.