I am thinking that the 1914 passenger list has an error. It was that Magnhild's father was Casper Martinson, living in Sarpsborg. This is written on the passenger list from 8 Jul 1914, written for the departure from Oslo. On the list from 20 Jul 1914 upon their arrival in New York, it says Magnhild was born in Larvik.

Now, ignoring the comment about her father being Casper Martinsen......

We know that several documents says Magnhild was born 30 Jul 1891. We know her middle name is Bendikte. We know the passenger lists says she was born in Larvik and that her death record says she was from Porgrunn. We know she arrived in America in 1911 or 1912 and married soon after her arrival. This make me this she knew Olaf Ingebretsen before she left Norway, which would mean she would have to have lived in Oslo at some time.

Now, in the 1900 census for Oslo, we find Magnhild Hansen, born 1891 in Larvik, daughter of the widow Margit Hansen, born 1869 in Larvik:

http://digitalarkivet.no/cgi-win/webcens.exe?slag=visbase&am...

In the 1910 census for Porsgrunn, Telemark, we see the widow Margit Hansen, born 17 Oct 1869 in Larvik, living with her daughter, Magnhild Hansen, born 30 Jul 1891 in Larvik:

http://digitalarkivet.arkivverket.no/ft/person/pf01036514003...

So, we have Magnhild Hansen, born 30 Jul 1891 in Larvik, lived in Oslo for a time, whose last residence on Norway was Porsgrunn. I can't find her birth record in Larvik - or proof she left Norway in 1911-1912. Still, I think this may be the correct Magnhild.