We don't know how Cora died, just that she died at her uncle's home. From FindAGrave, we find that she was buried in the Green Lawn Cemetery in Columbus Ohio. The FindAGrave posting lists her birth as July 11, 1847 and a death date of December 5, 1847.
It must have been a sad day in the family.
At the residence of S. D. Preston, Columbus Ohio,
Cora A., infant daughter of W. B. and Angeline
Preston, aged about 4 months. [Vermont Patriot will
"DIED," Indiana State Sentinel (Indianapolis, Indiana), 10 December 1847; digital images, Library of Congress Chronicling America (http://chroniclingamerica.loc.gov/ : accessed 5 November 2014).
Find A Grave, Find A Grave, digital images (http://www.findagrave.com : accessed 5 November 2014), Cora C Preston, Find A Grave Memorial# 68307794