I can not make out final diagnosis but can help with few possibilities considering her age and symptoms.. just simple low hemoglobin. So check her hemoglobin levels. can be interstitial lung disease related to connective tissue disease... So check her with a pulmonologist and a chest Xray .. can be due to problem in heart valves. So consult a cardiologist.. . but also can be normal and may be you are just over worried.. follow up with reports if any more help needed ..