I did a little more digging and found I must have the wrong Isaac Allen. I saw a record on the net at this link: http://watervillegenealogy.com/Early%20Families/home.htmlhttp://watervillegenealogy.com/Early%20Families/home.html Elenoris listed and it states that she was married to John Hersey after (Joseph) Harmon died. Her age is listed as 42 in an 1850 census record, so you are correct that she cound not be Ezekiel Philbrooks daughter. If I were you, I would check the census records for New Gloucester and other towns in the area to see which Philbrooks were there in 1810 and 1820. And also in Waterville.
Sorry I can't help more. I also saw that Joseph Jrs wife was named Georgie and was from Massachusetts while I poked around. I'm afraid my resources are limited.