Google Sensory Integration Disorder - and of course, sensory disturbances can be present with ADD.......However, not hearing/having trouble comprehending what the teacher said can be very well be a part of faulty auditory processing (even if a hearing is fine)....
With sensory integration disorder, children may very well do no hear you - b/c they have millions of sounds streaming into their brain and causing all kinds of electric activity...It is just difficult to single out your voice/directions as everything else is so distracting.
I am almost certain that treating senses that are "off" is a starting point in treating many developmental/learning issues, including ADD, PDD, what have you.
her doc thinks she could have add and is being tested. -- your words
This is the key part of your posting. Until the results of the tests come back, I would think that the best you can do would be to support your daughter with patience. If your daughter does indeed suffer from ADD, then she is will require help in learning how to listen. Your family doctor should be able to help you in this case. Please let us know the results of the testing.