I'm so sorry, A1ways.
I guess your concern about your DD's health vastly outweighs your concerns about her academic future, but even when it comes to the AS level question, i have no answers.
I think the option for counting AS levels towards the final A level result ended a couple of years ago. I don't think there are any exceptions, none that I have heard of any way.
I do have experience of a DS who is doing a mixture: 1 AS + 3 A, but I'm not sure how this could be helpful. When he does the AS level, that will be the end of him studying that subject, unless he picks it up at university.
I can't help but think that although it is a terrible time to get ill, there has to be more plurality in the system than just saying game over. Look at all the people around these days who left school with no or minimal qualifications and went back when they were older and now have first degrees, and sometimes even PhDs.
So, it doesn't always depend on getting A levels when you are 17/18.
You need good advice, and that isn't going to come from a school that only know about A levels for 18 year olds. But all these people who become mature students must have got advice from somewhere, so it must surely be out there somewhere??