Hi @AChickenCalledDaal!
I work with schools, including doing some work on Uni Admissions. For Unis, History is a 'strong' subject, the other two less so. All Unis will accept all three subjects, though.
For studying, since the Michael Gove changes, History is especially content heavy, certainly according to our '2017' cohort, the first year to do the new syllabus as Year 13 examinees in Summer 2017. It is content heavy and doubly respected as such. Politics is content light in comparison, and so is Sociology. But the three are a good combination for any student interested in broad fields of Humanities studies, at A Level and at Uni.
The writing for A Level is - sadly - formulaic and can be learned; for exams, it is clinically targeted at the published Marks Schemes. ... Perhaps @Maireas, as a History teacher, has explained it more kindly.
ADD? Lots of students have 'conditions', at school and at Uni, many more than most people realise. Many go on to do well, across a range of subjects. ADD clearly needs support but need not take away unduly from studentship or scholarship or, indeed, life.We know countless examples of successful students who faced - and faced down - all sorts of learning, health and other life challenges. ... Some great practical advice from @Cowbells on this challenge.
History? Your daughter should chat to two teachers, including a History teacher who knows her as a History student. They will guide her. ... Ultimately, I would let her do the three subjects she wants to. Don't be surprised if she changes her mind more than once between now and the middle of her Year 12. All of this would be normal.
Finally, we see a lot of angst and stuff from Years 10 -13, especially our girls. In the end, although all the students and their families do have ups and downs, it generally does all work out.