Getting a model to hit same exact mark I am trying to see if there's a term for what I'm about to explain or a better way of doing this.  Basically, my company is filming an actor from the waist up for short, 1 or 2 sentence clips.  These clips need to be strung together to look as seamless as possible.

The main problem is that the model has to rely on muscle memory to remember where her head (specifically eyes, nose, mouth) and shoulders are in the frame.

My solution would be to use a mirror with a hole cut out for a camera lens.  On the mirror would be marks showing where her features should return to after she says something. 

Is this typical, or is there a better way to do this? Or possibly to have another monitor with an overlay of the original position on it?  

I'd just like to try to make sure she doesn't constantly look away from the camera to achieve this.

Any thoughts?
One option, if you don't mind the actor keeping her head still, is to be partially lying down. She could be in a recliner, leaning back, with her head against the headrest so she never moves it.  She would feel the headrest behind her so she could tell if she'd turned her head, and it wouldn't "drift" left or right because the friction of the headrest would keep it in place.

Of course you would want to shoot all her lines in as short a session as possible so she didn't get uncomfortable - like 5 minutes for all the lines and retakes.