Hello Roger -
What I know about Cecilia (aka Sillie) is very little. Cecilia is my GG-Aunt, older sister of G-Grandfather, Johan HEGG. She was the daughter of Ole Hanson HEGG and Kari Arnesdatter LINNEVOLD. Cecilia was born June 1, 1833 in (or near) Lier, Buskerud, Norway. She died (abt) Jan 1, 1900 at the age of 66. Cecilia was married, first to Mr. DANIELSON and then to Hans Evansen SIVESIND. I believe that Cecilia (and Hans) had one biological daugher, Theodora SIVESIND.
As for Cecilia's surname ... if we use the Norwegian naming pattern, she would be Cecilia OLESON. (Her father would have been Ole HANSON.) IF we were to use the American naming pattern, she would be Cecilia HEGG. When she married Hans she would have been Mrs. Cecilia DANIELSON. [Does this make sence?]
Please, what is your link to Cecilia? Is your wife a decendent of Han's and Cecilia's daughter?