How to confirm right lower abdominal pain as appendix pain?

Hi doctor,

My 8 year old daughter has had quite severe stomach pain since three days. It started in her naval and now in her lower abdomen on the right hand side. She has had on and off low grade temperature and nausea. She has pain in her legs and some pain in her back. Also she has lost her appetite. We have been to our GP who sent us to our local hospital and they discharged us after blood tests were normal. She did have white cells in urine, and told us to come back if she was in agony. She is still having pain and has temperature. My dad is a retired GP and thinks that the pain is where her appendix are. Should I go to another hospital to scan her to make sure? I do not want to leave this to get it worse. I would appreciate your advice. Thank you.