Hi, I had gone through your question and understand your concerns. Fatigue in Ankylosing spondylitis is one of the most common complaints among these patients. Excessive tiredness can be attributed to AS itself, but it can also be a side effect. Treating inflammation with medications can help reduce related excessive fatigue. But also,prescription drugs that contain opioids or codeine may increase tiredness. However, if there is recent deterioentation of her symptoms and this sleepiness is cinderning sign, then other causes should be considered. Fatigue is one of the first signs of anemia or carotid vessels atherosclerosis so it would be good to see neurologist to rule this out. Wish you good health. Kindly regards