I'm afraid I'm going to have to disagree with Chainsaw Willie on this one.
The woman has been playing barely six months now, and she's just starting to really get a feel for what she needs to be doing. The last thing she needs is to concern herself with performance issues or her "game face".
What she is just now learning is to quiet the distracting parts of her mind, like her visual cortex. This is what's responsible for the "thereminists stare", or as she put it, a feeling of "daydreaming". It is a necessary part of learning to play the theremin well for many people.
I have only a limited knowledge of it, but what she needs is more of an extension of her yoga experience - to clear her mind of flotsam, and allow her ears, mind, and body to become one so they can play the beautiful music she hears in her head.
I had to go plug in my Etherwave to find out just what I do look at when I'm playing. I never watch my hands, but my mind does sense them using my peripheral vision. Occasionally, I look directly at the pitch antenna, but mostly my eyes are focused (subconsciously) on whatever is in front of me. I can move my eyes around, but I'm not wholly aware of what I'm looking at.
My focus is entirely on what I am hearing and what I know my body needs to do to play melody, phrasing, and dynamics.
However, I don't think it would do her any harm at this point to occasionally play for her kitty, hubby, or friends. If you could find one, you could get a large poster of some crowd scene (http://bandthenorth.files.wordpress.com/2008/01/plymouth-crowd.jpg) and tack it on the wall in front of you. Perhaps subliminally it could aid you in lessening any performance anxiety in the future.