While I don't know specificly Miss Reynolds as of Aug. of 1864 their were 173 citizens being held at Alton along with 1086 confederate pow's. March 9,1865 250 soldiers and civilians were held at Alton under sentence of military commission or court marshal.
Sanitary report of Aug.1864 says the facility had excellent records with only a 1 1/10 percent death rate.I would think these records would be availibable at National Archives or possibly Illinois State records.