Sinann,
You're right again. Harriett married James Reid and Elizabeth was living with them in Dublin in 1911.
I'm, also confused about the 1908 family address given as 27 Essex Quay in Maryborough. There is a 27 Essex Quay in Dublin, however. Also confusing is that only three months earlier, in August of 1908, Elizabeth's husband William died at 13 Ranelagh Avenue in Rathmines /Dublin.
In 1901, the family was living at house 8 on Stradabally Road in Maryborough. In 1911, Elizabeth was living with her daughter, Harriet, and family in Dublin.
I think Maryborough is an error on the part of the person writing up the record, Sarah says her last residence is Maryborough and I think they assumed this was where her mother lived, it's likely Elizabeth and William had moved to Dublin, moving around their children's homes, we still can't be sure we have found all their children.
If Elizabeth did manage to have children from c1859 to c1879, which is fairly normal for the time than there is possibly several more children.