Our grand daughter  had scarlet fever at 18 mos with fever reaching  107. Now at 3 she is still not talking.  She has been evaluated and autism is ruled out.  Can the high fever have caused brain damage to the speech center and if so can it be repaired, rewired so to speak?  She is happy and loving and will do what is asked of her (if she feels like it!)  She also had ear infections many times and had tubes put in her ears.  The hearing tests confirm that she can hear all tones.  She makes sounds and lets her wants be known!  But no words.  ?????
Delayed speech need not be an abnormal feature in most child Chat Doctor.  Sure, high fever can affect the brain, but it seems your granddaughter did not have any immediate effects of that episode of high fever. Hence, you should probably just wait a while before getting panicky about this. If she is still unable to talk at 3.5 years, please take her to a speech therapist. I assume that she is otherwise gaining milestones of movement, understanding etc. at the normal ages. Best wishes,