This Mistress is clearly experienced at training sissies to be Her slave. The sissy laying on the bed is an advanced sissy, and is helping Mistress teach a new slave.
On her knees - as she should be - the newbie is getting her first taste of cock. A taste she will, no doubt, become accustomed to, as frequent blow job for male suitors is surely in her future.
After this portion of today's training Mistress will reinforce the session by giving the newbie the strap on.
Alas, i am an experienced and well trained sissy. Even though this is the case, i'd much rather be the new sissy on her knees. Yes, i have been trained to suck cock - by Mistress Cassie.
And, i still serve Her........
sissy maid diane