It’s an awful age and an awful time and CAMHS is over stretched and may not have provided the right sort of help anyway . I know many many teens to whom this has happened, from year 12 to first year Uni. And lots at this exact point.
I don’t know if private counselling is an option? Also , ADHD is often a co-morbidity with ASD and round here it’s faster to get a dx for it; if she is ADHD there are anti anxiety and focusing medications, successors to Ritalin in a non technical sense, that can work wonders. Or not.
I think a gap year sounds right. Takes the pressure off while she finds an equilibrium. I’d expect her to work and contribute, but not in a this is the beginning of your career sort of way.
You sound great. Just continue to encourage her to do what she can, point out how great the summer will be after exams, point out that nothing is irreversible, there are no wrong answers at her age, that people who tell her she must do x or y or z are silly, save that gett8ng some qualifications at this point is helpful.
Are there social issues going on? Can you have a long car journey, no eye contact, to open the flood gates? Sometimes it takes 2plus hours, 150 Miles...