Hi, I think it would depend on how active she is? One way of working it out would be to get her to tot up the average cals she consumes at the moment, then drop that by around 500 a day. Just a rough guesstimate, but I think at her height and weight she could comfortably take off 1-2lbs a week in the initial stages by eating 1500 a day, more if she's regularly exercising.