I've seen people with seemingly NO talent for music or coding or whatever turn themselves into virtuosos because they WANTED it. It seems like saying "You need talent" is a way to tell people that "it's okay that you're not trying, because you might not be talented in this area". And that's bullshit.
It's much easier to get good at something you have a natural inclination towards. This does not mean that talent is a prerequisite for getting good at something.
And besides, having talent is like having a small head start in a marathon. You may start faster but that doesn't mean you'll finish faster.
Physical is easier to measure, but mental is just as real.
Natural talent counts for something, but it's not going to make you a success. I saw "result = talent * effort" mentioned on the last HN post about this, and I thought it was pretty accurate.
Also, and I don't know whether this is the case with your ex, it's entirely possible that she was better at art because she'd been idly drawing over the years. I've certainly known people who wouldn't call themselves artists whose default idle activity is to sketch away on a piece of paper. They're vastly better than me, because they've been practicing in a low-key way for years.
Natural talent just gives you a head start on others. Someone willing to put in more effort than you can still be better than you.
I suppose this may break down around the limits of a field, especially one rooted in physical activity. E.g. Michael Phelps seems to be nearly perfectly physically adapted for swimming. If he never practiced then he'd be easily outswum by anyone half-decent... but by putting in massive effort training he reaches a point where he's practically unbeatable.