Suggest Treatment For Swollen Ankle, Fatigue, Sore Knees And Neck

Hi, my daughter is only 14 and a half. She has a swollen ankle and also suffers from fatique. My doctor did a rheumatoid factor blood test that was negative. (I have rheumatoid arthritis.) She also had sore knees, a sore neck and pain in her fingers. I am very worried. What would the next step be?