Live Anderson/Lena Olsen

I am still having trouble locating who my great grandmothers parents were. Her marriage record to Riulf Olai Anderson July 1/1881 Moorehead, Minnesota shows her as Lena Olsen but they all called her the Levorsen girl. There are no records. Her gravestone says Live Anderson- she is born Dec 18/1858 and died May 9/1900. I know she died from childbirth complications and is buried in Rollag Minnesota. She had Alfred who died as a small child and then she had my grandma Hattie Alphine and "Alphine's" brothers Walter and Lester. I have seen that she was listed as born Norway and same for her parents on some of the cencuses. How can I get this figured out. There was also another Lena Olsen who married an Olai in the area too but she is living after 1900... I just want to find out her her family was??