Christie/Chasten Louisa Mattes/Mattis

I have reason to believe that a Christie Louisa Mattes is my g-g-grandmother. She married my g-g-grandfather, Peter Ondell, in Whitewater, Walworth County, Wisconsin. Peter was there in a boarding house alone in 1850 according to the census. Other records show the first two of the four children born in Milwaukee, which in near by. Whitewater was quite primitive in 1850 and many wives apparently lived in Milwaukee, while the husbands worked around there. The Wisconsin Archives lists the marriage date as April 18, 1851. The original hand written "certificate" is difficult to read and the date looks like 1857, but I am not an expert with the script. The name is slighlty difficult to real accurately, but seems to be reasonanly accurate for the time. The witnesses were Caroline Talloof and Talloof Talloof? She also apparently shows up in the 1860 U.S. Census as a "Chasten Ollendorf", wife of Peter was listed as "Peter Ollendorf". The children's names and ages were correct (and agree with all other documents), except fot the family name in 1860 census only. The address was also correct and agreed with 1870 and 1880. Apparently, the census taker was a first generation with a different language than the first generation residents. In the census, Christie's birth was shown as being in Norway in 1814. There was no mention of her after the census and Peter remarried in the 1860's I have looked at some sources for her, but she left Norway before the 1860 Census. I am trying to determine what her actual name may have been, so I can look elsewhere. I looked for the witnesses since they may have been related or from the same area/farm. No luck so far on the witnesses. I have no idea where in Norway Peter Ondell came from. The death records in that part of Wisconsin were very poor at the time and the is nothing in the archives or local cemeteries. Since I must assume she was from Norway, I would appreciate any help on possible Norwegian names since Mattis or Mattes do not seem Norwegian, but it could be Mathiasson or Matthewsson or ??? I am in Minneapolis/St. Paul and have access to many fine Family History Centers and very good libraries. If necessary, I will buy a service (Ancestry, etc. if necessary), but I need to know what to look for since I have plenty of time. Thanks in advance for any assistance. Dick