"Mr. Nathaniel Hubbard and Mrs. Elizabeth Nellson were married by Mr. Frances Macamy (sp?) 23d August 1707"
(Source: Massachusetts, Town and Vital Records, 1620-1988, Braintree Records, p 721)
Her name is given as Elizabeth in the marriage record and Eliza in the children's birth records. I have roughly estimated her birth year.
She could not have been the daughter of Rebecca Gore who married Nathaniel Hubbard in 1726. I believe Elizabeth and all her siblings (that I know of) were children of Nathaniel's first wife.
She is mentioned as a daughter in the 1747 will of her father Nathaniel Hubbard; the will also mentions two of her sons, William and Nathaniel. This suggests that her son Richard may have died by the date of the will.
I am not sure of this date for Elizabeth's death. Ezra Stiles mentions the death of a "Mrs. Munday" in June 1773, so it may refer to Richard's widow (source: research from Cherry Fletcher Bamberg, RIGS).