Annie DONNELL, a widow in 1900 Brooklyn, NY census, with 4 of 7 children living, Annie 18, William 16, Mattie (Martha)10 and Robert 8 (my son-in-law's grandfather), gave age as 45, b. Dec. 1854, immigration from Ireland in 1872.In 1910 she gave age as 60 and immigration as 1879. She does not show up in the 1920 census, but is mentioned on Robert's WW1 draft registration card (he says merely "mother wife 2 ch".)
I haven't found her husband's first name, except that the only Annie DONNELL on the immigration lists I've found came from Ireland with husband Michael May 20, 1880 on the ship "Erin", according to the Castle Garden website. They do not appear in the 1880 census. If Annie came as a single woman earlier, either in 1872 or 1879, I have no way of knowing which of the numerous "Annie" women of appropriate age might be the right one.