Hi welcome to the health care magic Your daughter having generalised pain for which HB estimation should be done as anemia can lead weakness Thyroid problem also should be ruled out If she is suffering from anxiety problem than also such weakness problem can occur... So avoid stress and for that anxiolytic drugs and behavioural therapy useful USG and chest x ray can be done If needed after examination If no specific cause found than it could be fibromyalgia or chronic fatigue syndrome like presentation for which amitryptillin given Take care Consult physician for examination