Sounds to me like you need to sit down with her and work out a fee schedule for both her and the outside customers. Expectations need to be expressed on both sides and decisions need to be made as to whether it is worthwhile or not. She wants a discount but a discount from what price? Does she have an expectations for priority handling of cases over outside customers and will that interfere with your capacity to generate business? Do you have the capacity to make a good living from this business? In my experience, even in-house labs work best in an "arms length" environment. If you end up having to drop everything to take a shade several times per day and make minute adjustment to every crown that would otherwise be seated, it isn't going to make sense. You should ask numerous questions and have the answers clearly defined. Its like a marriage...go into it with your eyes wide open!