When people say "she already has everything," they usually mean things. But experiences, impressions, and the chance to try something new - that's a whole different level of gift, especially for a practical person. Within your budget, you can really pull off something interesting.
Think about gift certificates for masterclasses or courses in something she's been curious about but would never start on her own. It could be anything - from a cooking course if she loves to cook, to pottery, photography, or even sailing lessons. The thing is, she'll get not just an object, but a reason to step out of her comfort zone and pick up a new skill. This kind of gift unfolds over more than one day, which is really symbolic for a milestone birthday.
Another option is a spa or wellness package with a few treatments (you could go with a nice spa center that has comprehensive packages). It sounds like relaxation, but it's actually a practical gift: taking care of your health is never a bad call. Or a weekend gastronomic tour, wine tasting with a guided excursion, a couple-day trip to a neighboring region - something she'll definitely make time for but wouldn't organize herself.