Caroline Nilsen of Drammen, b~1860

My great grand-mother was widowed with four children under the age of 12. She was institutionalized with what we now believe was post-partum depression. I have very little information on her other than what is listed on her marriage license. Her Marriage license, dated 4th of May, 1881 in Cook County Illinois lists her father's name as Hans Nilsen and her mother as Ann or Anne Karine Andersdotter. She was to be 21 on her next birthday, so her birthdate should be between May 5, 1859 and May 4, 1860. The place of birth is listed as Drammen, Norway. I have found several Caroline's born in the time frame, but none to these parents. I have wondered if she lied about her age in order to marry; if so, she may have been born up to 1862 or so. I assumed she emigrated not long before she married, so I have only searched ships records for 1878-1880. While I found some listings, none give clues to her family of origin, which is what I would really like. I realize this is scant information. Any help you can give to find Caroline's family of origin would be appreciated. She died after a decade in the asylum to which she was sent when her husband died and her children were split up and adopted out. Her health improved eventually, but by the time she would have been able to go home, there was no home to go to. I would like to honor this woman by trying to reconnect her with some family. Thank you for your help.