Nothing will withstand prolonged exposure to UV rays. You have a few options; keep the blinds closed when the sun hits the windows, replace the windows with new ones that have a UV blocking glass, or you can put something outside that blocks the sunlight such as an arbour or louvers or even a tree. Anything to block the sunlight. This will have the added benefit of reducing heat gain in your house during summer months.

matchstick/bamboo blinds
sisal rugs
plants
slip covers
inspiration room

Perhaps rattan or wicker chairs/loveseat that can withstand the light? You can add cushions for comfort and color. I like the idea of matchstick blinds or roman shades for light control. A sofa back table where your current couch is would add a service for plants and artwork. I think you might find it a relaxing retreat if you treat it more like an indoor patio/garden room. Consider tile for the floor - it will not fade in the sun like wood or carpet will. There are even some beautiful wood-look options available in tile.

Be sure to use Sunbrella fabric on the furniture.