Helen Seymour Sylvester Attended Vassar

It appears that our mysterious founder and builder of Seymour Point, now called Penwood, Helen Seymour Sylvester, attended Vassar College in Poughkeepsie, New York, beginning in its first year, 1865.  Letters betwen Helen and her family are part of the Vassar College archives.  I would love to read them but they are not available online.