That certainly seems possible. Having only attained the lofty rank of SP5 (E-5) in the Army I know very little about the service academies. But if she was a "freshman" she would have only started days ago. I know that the academies start rigorous PT very early so it seems possible that she,as a result of that PT,had some kind of undetected heart condition that killed her.
Like I said...the family should get an independent autopsy.