She might have arthritis, aggravated by a slip on the floor, OP.

^sorry for the spelling errors

I don't have any advice about the floors, but I think you have gotten some good sugestions. My dog has anxiety during thunderstorms as well and I wanted to add that we ordered her a thundershirt and she loves it! Really helps with her anxiety in general, not just storms.

http://www.thundershirt.com/?gclid=COyusd6HtLUCFQjf4Aod93MALA

Consider getting some small area rugs, carpet remnants and runners that can be put out for the dog. Many bigger dogs are afraid of slipping on surfaces like ceramic and hardwood. If these are smaller, you can pick them up and put them in the garage or basement or storage when company is coming over and then put them out for the dog in between. It doesn't have to be everywhere, but just in areas where she walks regularly (her favorite room to the food bowl in the kitchen, for example).

One of my dogs did this when her nails got too long, when she got older. Possibly a trim would help. But yeah some dogs just have a phobia about that type of flooring.