My Grandmother - Borghild Hunn

This is my second post. My first was very successful thanks to "eibache." I'm hoping someone can find this piece of my heritage puzzle, as well. My grandmother was Borghild Hunn, married to Peter (sometimes "Petter") Hunn. I understand from my Norwegian cousins that her maiden name was Borgen. I have been unable to find her parents or any information about a family named Borgen with a daughter named Borghild, so I'm hoping for help with that. The family lived on a farm named Bustgard (which I believe is in Ostfold), and later the family moved to Sarpsborg where my grandfather worked in a bank. If there's any other information that I can supply that might help, please let me know, but I have shamefully little information about her! Thank you.