Eliza J. Haynes

Eliza J. Haynes, daughter of Asa Haynes Jr. and Sarah Rice was born about 1815 in Mass. About 1836 she married Robert McFarland in Mercer County, Pennsylvania..I have them well documented on census records and death records. What I need proof of is, is the Eliza who married Robert McFarland, the same Eliza daughter of Asa and Sarah?? The May Flower Society wants documentation that they are the same. I cannot find a Marriage Record of any sort. Help is greatly appreciated.