My grandmothers maiden name was Hjelle. As it turned out Hjelle is the farm name where they came from. I wouldn't be surprised if Brostalaken actually is the farm name of where Oline came from as well. My grandmother came from around Sogne og Fjorde and they were excellent record keepers. You might have success finding help on the digital archives of Norway which provide a great deal of Information on line. There are several other sites if you interested. Just let me know if you would like them. Good luck in your search.