Specifically to a level? No. But I did do it at degree.
Generally speaking it's the history of the world taught via art. At degree level we (at Leicester) studied cavemen to the Renaissance in the first year. Second year covered Renaissance to modern times. Third year becomes specialised. It traces the development of man, development of countries, development of belief systems. It covers art, architecture, crafts, spiritualism and literature. Royals to medicine. It will cover feminism, modernity, wars, post wars, and art theory. That special language reserved for reverence of The Turner prize (
) etc.
At degree level it often includes travel. We went to Italy for example.
I'm biased but I love it. So many things have related to it in my life. As a life knowledge broadener Id recommend the subject wholeheartedly.
And definitely Leics. Uni 
Do read the school curriculum. That will be the best source material immediately. It is most certainly an essay subject. She will develop critical ability. It will show her how to build arguements and persuade through her writing.
Word of caution, it's not a 'cop out'. If she's looking for an easy subject she may not like it. Art often sounds simple. People can be disappointed when they discover it's not just looking at pretty pictures....