Going through assessment and eating disorder

Hi, my daughter was recently assessed for an eating disorder, as she had dropped to 82% of her recommended weight and was /is obsessing about calories, weight, being slim and exercising. Five weeks later, she has only put on 700g and is trying hard to put weight on but still struggling and has an overwhelming obsession with food/exercise. 

During our assessment, the eating disorder nurse suddenly told me they think Katie has HFA an that there is no mental health issue, it's all to do with rigid thinking and that food and health are her special interests. I do know she has a few traits, but I don't agree that there's no eating disorder at all, she has many classic symptoms even if they are caused by autism. All sh talks about is eating healthily, is obsessed with helping me cook and won't eat chocolate unless she has decided maybe one day in ten to allow herself a treat day. But she does enjoy her main meals as long as they are healthy and she knows roughly what the calories are etc.

The paediatrician this week said she may be borderline so is sending us and school questionnaires. She'll use those to decide whether to do in depth assessments which could take a few months or possibly up to a year due to waiting lists. In the meantime, I am so anxious and upset trying to  encourage my D t eat more and dreading the weekly weigh! At least she's not losing weight now but her arms are so thin and she just isn't her usual self. I am ok most mornings, I work from home as a writer which has been flexible but also a little tough while I'm feeling like this. I would call the camhs nurse back but I don't think they will do anything as they say there's not a mental health issue. Only option I can think of if the weight doesn't go on well, is to self-refer via the anxiety route, as the ED is based on anxiety about getting fat and unhealthy.