I concur with Karin and LaRue. Once you correctly calculate her RMR, add in calories based on her activity level. Then subtract out 250 – 500 calories per day to help her achieve her weight loss goal.
However, like you pointed out before and Karin as well, there also needs to be an education of the client regarding the quality of the calories she’s consuming, that she needs to eat to her activity level, that reducing calories too low will slow her metabolism and that she needs to add in a full exercise routine (cardio, strength training and flexibility).
I often have clients judge their health not just by a number on a scale, but also by waist measurement, body fat % and how their clothing feels. They can sometimes see these numbers improve before the number on the scale changes.