I'll second the people who say you shouldn't be making gear decisions for someone who's into their hobby. That said, there are things you can do beyond simple gift cards.

Sleeves of balls. If you don't want to risk a surprise, go check what she's already got. I haven't played a round of golf in almost twenty years, but they're effectively consumables, so even if you don't get her the dream ball she's after, they'll get used up on casual rounds or drops after going into a water hazard, that sort of thing.

Personalized ball marker for putting greens. This can be done really cheap if you have access to a laser cutter or 3D printer, and could go really well as a "sweetener" to personalize a gift card style purchase. Even if it doesn't become her main marker, it'll likely live in her bag and make her smile without taking up much space.

Same for tees, though you're more likely to have to get thought from elsewhere. Just take a quick peek in her bag again to see the length and material (wood or plastic) she prefers. These are also consumable, but the initial drive from the tee is a more controlled shot so she's more likely to want her preferred style.

Experiences: time at a Top Golf style place or traditional driving range, pre-paid greens fees for some nice course nearby or one of her favorites, lessons (if and only if she's mentioned it!). Does she have a favorite golfer or is she into internet culture surrounding golf? If so, you might find a Cameo from a minor celebrity is a surprisingly memorable purchase.

Time: Has she implied that she'd like to share this hobby with you? If so, volunteer to go with her and treat her like the expert she is. Has she not asked, but you are a person in her life who can make demands on her time? If so, then explicitly give her more time, including some that you would normally claim.