My DD's school have been amazing too. She missed the first term of y10 almost entirely. They provided her with the lesson notes and any work but she was told she didn't have to do any of it if she wasn't up to. Mostly she didn't. The head of year kept stressing that we weren't to worry about academics, they'd sort themselves out. We were a bit sceptical but decided to go with it and they were completely right. She caught up and then some once she was eating OK (and only OK, she was still low weight). The rest of the year she was missing at least two afternoons a week.
To generalise massively, often the very characteristics that makes some girls prone to anorexia are the very things that make them academic high achievers. Of course not always etc, etc, but in DD's case, she's very conscientious. Her revision notes are works of art, like the anorexic brain on a page.
The school also suggested that she apply for rest breaks in exams - not extra time, but little ten minute breaks every hour if she wants them. Although she's much better, this will be in place for GSCEs. We got a letter from the psychiatrist for this.
She also decided to drop a GSCE, art, because it was stressing her. She's still doing 9 and will likely do further maths, so it's more than enough. I'd have been happy for her to drop another.
Oh the other thing was that the teachers really love-bombed her too. Parents' evening was full of praise even from teachers who'd barely seen her. I think they'd been told to do so.