Well, if she likes fitness maybe there's a new exercise machine as wedding anniversary gift
she might like? Or how about a membership or gift certificate to a health spa?
Another idea is a ring with an inlay of wood, If you google "wooden inlay wedding rings" there are a ton that come up.
For our fifth anniversary me and my other half are planning a nice trip together.
Or you could always break down and ask her. Something like " Honey, I want to make this anniversary really special. Is there anything in particular you would like?" Personally I always appreciate being asked questions like that and maybe she has a really good idea.