I was a jack of all trades master of none. I wanted to do single sciences, maths, English lit, geography, history and art by time I got to a level. I had no fucking idea what I wanted to do. I chose my uni degree by picking where I wanted to go first, then looking through every course and deciding what I DIDN'T want to do. It was totally backwards and utterly ridiculous. Your daughter doesn't sound a million miles off my mentality.
I did art and history at a-level. I did media and history at degree with some art history mixed in to boot. Then ended up working at a printers doing graphic design.
This is my take on it.
I'd say 100% do the history. At GCSE level art involves more work than history. And it's not the end of the world to lose.
I was good at art, but there were times it felt like an absolute chore - and I loved it. If anything it made me dislike it at times. You have to be really committed to the art imho. At a level I loved it but not enough and certainly it wasn't my passion. And there's zillions of ways to pick it up later without having done it previously. Having worked in a printers, having it on your CV really wasn't terribly helpful - the kids who came in for jobs had no concept of deadlines. It was all pretty pictures and often not much else ticking upstairs. And all employers were really interested in was a good portfolio and evidence you had the correct skills for the job which you can show without a qualification for art. Given that all my graphic design stuff was self taught and not from formal education it kind of makes something of a joke of it. Actually having a degree in something more academic was more useful in demonstrating my worth. It said I could do more than pretty pictures and had some intelligence too.
Careers in art either go down the REALLY creative path (in which case her talent and passion would be driving her in a single minded way now) as it's competitive and difficult to make a mark in OR you go more down the marketing type route of understanding visuals, meaning, significance and message. In which case history / politics / media actually gives you a lot more of those type of skills in terms of being to analyze content - and do the reverse of create content. History is a solid entry to all three.
She not an artist in the making by the sound of it as the passion she needs for it just isn't there. Maybe a creative career but not artist. Or if there is a massive shift there are pathways to that (foundation course being the most obvious). So if she's about keeping things open history is probably a better choice even if she's likes the art on the side.
Maybe others will have a different take but that's where I'd be looking at guiding her