Anna Andreassen

I am trying to figure who Anna Andreassen was. My great grandmother Martha Ensrud, later Julseth had letters from her and even some pictures. She was from Oslo, Norway and Martha was from Gran, Norway, but went to America in 1904. Apparently Anna visited her at least once and had relatives in New York. I know this information is pretty vague, but I would like to try to figure who she was and if there is any connection as far as relations go! Thanks Tim