Well doing any A-Level in one year might be a bit of a stretch. Who is it that suggested she would be able to take it in a year?
I'll give you a personal anecdote that might help:
I started Year 12 doing History, Law, French and Spanish.
Half way through Year 12 I decided to drop History and Law. So I finished Year 12 just having done AS Levels in French and Spanish.
I then took up Classical Civilisation at the start of Year 13. So by the end of Year 13 I'd finished French and Spanish, and also had an AS in Classical Civilisation.
I then stayed on an extra year and did Year 13 a second time. I finished off the second year of Classical Civilisation, and just to make up hours in my timetable I also resat French (taking it from a C up to a B), and did GCSE Italian.
So yes it's perfectly possible to take Class Civ up in Year 13, but I'm far less convinced that your daughter's college will allow her to do the whole two year course in just one year.