Nils Pedersen family, Sesseng farm in Selbu

I am getting desperate trying to find my Grandmother's family. I know she went by Ingeborg (Inga) Nelson here in America before marrying my grandfather John A. Anderson. Ingeborg was born on Sept 18, 1878 (maybe in Trodjeon) in Norway. She came to America (according to the US census) in 1897 and settled in Buffalo, North Dakota where she lived most of her life here. I have talked with family members and they don't seem to know anything about her other than what I have stated (I have a hard time believing they don't but that is what they say). I don't know how many sisters and brothers she had although I know there were a couple (I only have heard of sisters) and I am trying to find out more about them but so far finding very little other than who they were here and that they also went by Nelson before marrying? What do I do next? I have sent for Grandmother's marriage license, death certificate and looked at all the census we have here and I cannot find anything more about her. Because of the great people on this site translating my Grandfather's letter edged in black, I have traced Grandfather back a couple of generations in Sweden now and that has been exciting but I can't get anywhere with Grandmother and I don't know what to do next. I still have several letters out to family members that lived around Buffalo when Grandmother was still alive but they were very young--still hoping they remember some stories or something though. Thanks for any help you can come up with. I am about out of things to try. We are still looking through Mom's stuff hoping to find something but so far nothing about her mother and family. Debra