Anna Christina Ingebretson b. 1808

Anna was my great, great grandfather's sister--he being Lars Ingebrightson b. 1799 at Kallevig/ Kallevik, Avaldsnes. Anna was born 1808 page 43 of Avaldnes in Avaldsnes 1801-1817. I can't seem to find a confirmation or death record on her. I did find an 1865 census that might be her living with an Elias Johannes and his son on Rabben, Kallevig farm. And also her in 1875. A few years ago I found her with the son, Elias who had married. Then nothing. Is this her or do I have the wrong person? A letter from my ggreat grandfather to his brother in the 1870's lists a Christine coming and then she got married in the Webster County, Iowa USA area. This is the only possible Christine I can think of. Need help badly Lorene