Not cheating, but a family upgrade: my beloved mother wants a threesome

The little girl often had the same nightmare: her boyfriend in bed with another woman. But as soon as she realized that the other woman was her mother, she understood that she urgently needed to see a psychologist. Or maybe it was a prophetic dream? No, that's nonsense. Although, why is her mother sitting in the living room with her husband for so long, when they couldn't even stand to be together for a couple of minutes before? She needs to go and check everything out...