Olsen or Ohlsen Christiansand to Minnesota

I am searching for emigration date and ship for Ellen Olsen or Ohlsen, born 1862 in Christiansand and emigrated to Minnesota in about 1880, give or take a few years. She lived in Minnesota for about a year or two, then moved on to Dakota territory, where she was perhaps the first woman to homestead in that territory. I'm also interested in information about her family. I have one postcard picturing two people, most likely her relatives from back home (both male).