The girl's attempts were not too bad, actually.  She seemed to be attempting to mimic what she felt, which to Yvette, spoke volumes.  She had real potential to become one of her pets.  Without warning, her arm around the girl's waist moved, her fingers sweeping Lin's juices over her other hole, not applying any real pressure or trying to penetrate, just brushing it, teasing it lightly.  If she were going to be a proper slave, she had to learn that her entire body was meant to be used for Master and Mistress' pleasure, not just one place or the other, but some things required a slower introduction, to ensure that she loved giving herself completely and without question.