Boxed in
 

That's got to be tough working daily with someone always looking over your shoulder.~ :eatinghersheybar:

Have your co-worker switch seats with you. Sit in her desk and have her sit in yours and then ask her if she can see anything that you are doing at the PC.

Also, ask if she still feels uncomfortable what you can do to ease her mind keeping in mind that for your own health you don't want to have your heart startled when someone approaches you from behind. See what she says and work from there. A reasonable compromise has to be made otherwise the other option is to have her switch seats with someone else who has no issue with this.

Good luck!!

She wound up quitting years ago, and thankfully we aren't as tightly packed as we once were.