I started my career in university admissions, and although it was more than a decade ago, gained good insight. I don’t recommend FM if it comes with only two others from the outset. There is a really big jump from GCSE to A Level in maths and students who are strong sometimes struggle. Colleges teach it differently which also makes a difference - some do M and FM in parallel and some do sequentially, and some do different mixes of modules.
I started with five: chem, bio, physics, maths and further maths. I had a terrible maths teacher, did ok at maths, but tanked FM and ultimately dropped both into my second year. (I had 8 A* and one A at GCSE, with A *in maths and science). I might have done better at maths with a better teacher, but I also had a massive crush on the boy next to me, so, was distracted.
I think EPQ is a great thing to do, particularly for preparing for more essay based subjects. It focuses students on broad research skills and also how to form an argument, but it’s largely independent learning and takes a lot of time for students to master (and thinking among my friendship circle, I think those students who do well may have quite a bit of parental support). So it might not be the right thing for your child, unless she picked a topic related to her sport, which she could.
I like the suggestion of PE or maybe human biology - these are good options for sporty kids, and studying sport and exercise science (which is now quite a serious and in demand topic) or engineering with a view to working in sports engineering sound like good career choices.
I’d also recommend caution on the sport being the be all and end all. I knew a lot of talented athletes at uni and few of them compete now - plenty of them competing at national and international levels as teens. I also knew Helen Glover vaguely as a teen, who famously didn’t find rowing until after uni. My recollection of her is that she was an outstanding athlete and it didn’t matter what the school sport was, if she was on that team, they were going to win.