i mean in thebook theres no orgy, she's just asleep in bed when geralt meets her, and later on when they bathe together, she puts an invisibility spell on herself so geralt can't peep.
In the second book of short stories their is a group sex event.(not a orgy) Geralt interrupts Yen and pretty much steals her away from her partner. I would say all the sex stuff is more the game series influence though.