It could be viral fever or dengue, chikungunia which is prevalent.  Consult a physician

Hi there understand your concern... There are many conditions which present with fever... Fever may be due to urinary tract infection, respiratory tract infection, gastroenteritis, malaria, typhoid, dengue, tuberculosis, viral infection etc...so detalied examination and evaluation is necessary... Take over the counter paracetamol 650 mg thrice daily and do tepid sponging...Consult nearest physician they will do the needful.

Hello there.  I can understand your concern.  It could be a viral fever. But since she is past 65yrs age, its better you get her checked out by a general physician in person for further evaluation and management.  As of now just give her a tab. Rantac-D half an hour before food. And tab. Zerodol-p after food. Best regards. Dr. Anil kumar jain. Bangalore.

Meet MD physician to rule out sinister causes of fever as systemic symptoms present