Agreed. For Nat 5, the OP's daughter really needs to attend school. At a push, it would be possible to tackle the English coursework at home, but it would still need to be printed off on the SQA template and submitted by the examination centre and the centre has to be confident that it's the pupil's own work so would need to see the plans, first drafts etc.
I really don't see how it would be possible to complete the coursework element of practical subjects at home. (Not my subject, but I'm aware that the coursework element in Chemistry is significant, for example.) I'm assuming that the daughter doesn't take Art, Drama, a M.F.L., Music or P.E. at Nat 5.
In addition to all of the above, the examination centre needs to submit estimates (unless things have changed drastically since I retired from middle management). I know that the SQA have made it nearly impossible to submit appeals these days, but - unless I'm completely out of the loop - the candidate is safer sitting a prelim which can be submitted in the case of illness or an accident on the day of the SQA exam.
It doesn't happen very often, but I recall one candidate having her leg set on the day of her exam and another having the tendons in his hand reattached (courtesy of a fish gutting mishap). They both got their passes awarded. if there had been no prelim or other proof of achievement under controlled conditions, they'd have received No Award.