The dietician phoned today. She's offered to weigh DD1 on Wednesday to see if she's lost weight since November. She pointed out that there's not masses she can do because she can't make DD1 eat.
I agreed with the dietician but also pointed out that although she's 5'4", her sisters (20 months and 3.4 years younger than her) are almost the same height, so DD1 is too short for our family. DH is 5'10" and I'm 5'8". DD2 is on the 75th centile for height and DD3 is almost 91st centile for height, so it should ring alarm bells that DD1 is only 50th centile. Also, her feet haven't grown in a few years. She's a size 3 foot size. DD2 (13) is 5½ pushing 6, and DD3 (11) is size 4.
The dietician did at least sound puzzled when she asked who DD1 was under and I said 'no-one'. I explained that the Consultant discharged as he didn't want to deal with ASD assessment (despite having a special interest in ASD). CAMHS referred to Psicon (ASD assessment centre) and discharged. Paeds in the summer referred to dietician and discharged.
The dietician was going to refer back to DD1's old paediatrician, but I suggested 'fresh eyes' might be wise, as her paediatrician wasn't interested in her. So she's going to email all the paediatricians and see who bites 
She said that they may need to admit her for assessment/monitoring/tube feeding if she's refusing to eat. But she has no power to do anything.
She did ask about periods and was pleased to hear that after a break of 2-3 months, DD1 had a period this month.
I don't think DD1 will have dropped her weight drastically - she's not exercising and she's already so light there can't be masses to lose. But my point is that she shouldn't be the weight she is in the first place.
I said to DH that I'm considering not pushing DD1 on food this week, so I can see what she will eat without encouragement/pressure from us. That way I'll be able to give an accurate picture to the dietician.