If it is feasible, I would see if the vet could test one of the chickens for that particular disease. If so, and you get a negative report, you could approach her and let her know that you understand her concern so you had it checked out. Give her a copy of the vets report to show that she doesn't have anything to worry about from your birds. Then I'd give her the printed info about the soil and wild birds. All delivered with some fresh eggs (if they started laying yet)
This way you don't encourage a bad neighbor situation which can spill into other things.
This way you don't encourage a bad neighbor situation which can spill into other things.