It was part of the game of Magic Time, something she learned from one of the Cytheria Coterie training manuals. It augmented her power and control over him. The Coterie taught her that keeping a man in an aroused state made him easier to control, and in Lanny's case made him more vulnerable to her whims and kinky desires. It helped release the inhibitions that he harbored about his own deviant inclinations. When excited he was easily encouraged to reveal the darker side of his sexual libido. Many men went to prostitutes to gratify their stranger sexual tastes because they were ashamed to admit their aberrant desires to their spouses.
If honor hadn't confronted Stella Finpoint at her condo that night, she might not have ever known about Lanny's secret inclinations, his penchant for submission, his bent for femininity. She thanked her lucky stars that Stella was a free spirit, that Stella was so bold and kinky herself to make a move on the wife of the man she'd been fucking. She had to thank Stella for her candidness and the Coterie for guidance.