This mistress could tell that this girl was a lesbian but it did not look like she knew she was one yet. So the mistress found a way to make him know. And it was by facesitting him and smothering his face with her hot ass. As she enjoyed the smell and texture of her ass, she was turned on and that is how she knew she was a lesbian.
When it comes to teaching people a lesson, few do it better than these mistresses. They know how to improvise and come up with a way to have fun at the expense of those they are humiliating and teaching a lesson. That is what happened today as they trampled and used all manner of humiliating punishments to torture this slave girl. They managed to have the fun they wanted and teach her a lesson at the same time.
When mistress Anna and her lesbian lover met this girl who was also lesbian but she had never had a threesome, they felt like they needed to make her experience some fun she had never experienced before since it was her birthday. The mistresses chose to dominate her and make her enjoy bondage first before they let her enjoy their pussies and them to enjoy hers. It was a magical time for all of them and especially her.