These would be girls in training, some of them perhaps White Silk Girls, being accustomed to the routines and techniques of serving at table.
Assassin of Gor Book 5 Page 88

A girl in a tunic of white silk, gracefully, carrying a large pitcher of diluted Ka-la-na wine, approached our table from the rear, and climbed the stairs, delicately, and as though timidly, head down. Then she leaned forward behind me, bending her knees slightly, her body graceful. Her voice in my ear was a whisper, an invitation. I looked at her. Her eyes met mine, beautiful, deep, gray. Her lips were slightly parted. "Wine, Master?" asked Virginia Kent.
"Yes," I said, "I will have wine."
Virginia served me, bowed her head and backed gracefully down the stairs behind me, then turned and hurried away.
"She is White Silk, of course," said Ho-Tu.
"I know," I said.
Assassin of Gor Book 5 Page 186

I was white silk!
It was safe to dance before them as I pleased.
And so Elinor Brinton danced to torment them.
They cried out with anguish and pleasure. How pleased I was in my power!
As the music changed so, too, did the dancer, and she became as one with the music, a frightened girl, new to the collar, a timid girl, delicate and submissive, a lonely slave, yearning for her master, a drunken wench, rejecting her slavery, a proud girl, determined to be defiant, a raw, red-silk slave, mad with the need for a masters touch.
Captive of Gor Book 7 Page 328