Things in education have changed massively over the last two decades.
However, as has been said, MiniMoon, your g.daughter is well along the path of her 'options'. such as they are.
She will be doing will doing the core (compulsory) subjects of English, Maths and Science (either double or triple), religious studies (under whatever name is given to it), a humanity (history or geography), an Arts. At the end of yer 11 she will sit these GCSE's.
As has also been said, once GCSE's are out of the way, either she can go onto A levels, or go to an FE College which will give a wider range of subjects, and exams.
You seem confused yourself, as to what you are asking. In the original OP you ask WHEN she will choose her options, then in your later post, you state she chose options when she commenced in February. If she has not been following the syllabus during her home schooling, then she may find some of the subjects difficult.
Her autism, hopefully, should not have too much of an problem. . If it is bad, and causes her real problems then she should be referred for assessment.
One of my G.sons has Autism, obtained a good clutch of GCSE's, (albeit at a special school for youngsters within this spectrum), and four A levels A, A, A, B at a local FE College, and is in his second year of chemical studies at Uni.