Birth Record for Mari Olsdatter from Fet/Rælingen

I'm looking for the birth record for a Mari Olsdatter who married Jørgen Amundsen of Løvenstad in 1811. They moved to Longelstad and had four children: Petrine, Anne Marie, Oline, and Henrich. According to the bygbedok for Rælingen (the section on Longelstad) and her burial record, Mari Olsdatter was born in approximately 1775. Their marriage record lists her location as Nerdrum. However, when I check the bygdebok for Fet and the 1801 Norwegian census, I can't find a Mari Olsdatter born on Nerdrum around the right time. Furthermore, I can't find any 1774-1776 birth records for Mari Olsdatter in the Fet church books. Does anybody have any ideas for what I should try next, or possibly any leads? Here is a link to their marriage record (third from the bottom on the right), and below is the bygdebok text. "Jørgen Amundsen fra Løvenstad 1783-1864 overtok kort tid etter. Jørgen og kona Mari Olsd. 1775-1832 hadde barna: Petrine f. 1815, Anne g.m. Nils Amundsen Dølahaugen, Oline f. 1819, Henrik f. 1821 g.m. Kari Hasd., se Korsveien under Åmot."