Welcome to HCM.
I understand your feelings, but it may not be possible to come to the right diagnosis always. A doctor makes provisional diagnosis based on presenting symptoms and clinical examination and depending on what he or she considers to be the problem may advise for further investigations to confirm or rule out those possibilities.Fever
can occur from numerous disease conditions and it may not be possible to pin point the correct cause immediately. Most of the times doctors treat fever on the line of diseases prevalent in that area and if the patient does not respond then they go in for further investigations. Most of the time the doctor's judgement is right and saves the patient the trouble and money for doing expensive and invasive tests. Have confidence in the doctor you consult and you will certainly get good results.
Wishing your mother speedy recovery.