Basil I really hope you have a good nurse who will fast track referral. I'm no expert but I've read a few times that taking to A&E speeds things up.
My dd is around 82% wfh - that's around 7 stone at 5 foot 6 age 16. She's eating 2000 calories a day and that only maintains her weight or gives a miniscule gain and that's with part time college dropped door to door and very little further activity. They need what feels like an enormous amount of food to them, to actually gain weight. It's a struggle to get more in but we're getting there at a snails pace and I'm learning to enrich every meal as much as I can without freaking her out.
At dds camhs assessment the therapist told dd that her body is failing and she may faint, have heart issues, hair falling out, dry peeling skin, break bones and may be unable to have children, no days out, no holidays and may die. I cried. It definitely got through to her. I have to remind her regularly (which kills me) but they need to know WHY they need a certain amount of food to avoid serious illness or worse.
Between the amazing group of people on here and the Facebook group I've learned so much more than through the camhs appointments which are mainly for her obs and to show dd that her illness is serious enough to have to attend weekly. There's a wealth of experience and support. I've got the Eva Musby book which is brilliant.
If your dd is open to it, I would start today sitting down together and writing down everything she eats right now and make a list of breakfasts, lunches, dinners and snacks that she enjoys. Use this to start a weekly meal plan. My dd responded well to this as she's extremely independent and needs some control and input into what she eats. I know it doesn't work for all.
Family based therapy of 3 meals olus 3 snacks is very simple but effective, even though it can take a while to get into the routine. My dd started on 1500 calories a day which she fought for a while, but even if it's not calorific enough at first it's good to get into the habit. You'll need to sit with her and eat the same. Then once she's into the routine of the 3 + 3 you can start making every meal the best that you can. I started with butter and cream in sauces in tiny amounts and slowly built up. I put olive oil in an old frylight bottle and use it liberally on pretty much everything - chicken nuggets soak up an enormous amount of oil. I do a bolognese, a curry and a carbonara with her portion coming in at 1000 calories. I can do hers separately because she doesn't like onions - luckily.
We're a few months in now and dds weight gain is very slow but her mental state and her willingness to get better is a million miles away from where she was.