Mike, I think the person that sent you the email is mistaken. Birger has both a sister named Gina and a wife named Gina.
His sister Gina Karoline Mikkelsen is baptized in Vestre Aker Church (really she was baptized in Sørkedalen Church) on July 12th 1891 as shown here in the Churchbook for Vestre Aker, no. 10, 1886 - 1903, page 96: https://www.digitalarkivet.no/kb20060830010087 She's the first on among the girls (bottom half) and her name is Gina Caroline. Parents: Husmand (Cotter) Gustav Borgersen and his wife Marie Eriksen. She was born May 23rd 1891 on the Bjørnsjødammen farm in Nordmarka in Aker county, now a part of Oslo.
Birger Gustavsen Bjørnholt is baptized in Sørkedalen Church June 11th 1893 as shown here in the Churchbook of Vestre Aker, same book as above, page 126: https://www.digitalarkivet.no/kb20060830010118 He's the first one among the boys (top half) and his name is Birger. Parents: Farmer (he's renting a farm) Gustav Borgersen and his wife Mari Eriksdatter. He was born February 20th 1893 on the Bjørnholt farm in Nordmarka in Aker county, now a part of Oslo.
Birger's wife Gina Kaspersdatter was baptized March 7th 1897 in Vestre Aker Church as shown here in the same churchbook as above, page 192: https://www.digitalarkivet.no/kb20060830010185 she is no. 17 name only Gina. Parents: Skovarbeider (woodsman) Kasper Hansen and his wife Hanna Mathilde Hansen. She was born January 29th 1897 on the Bonna farm in Nordmarka in Aker county, now a part of Oslo.
Bjørnsjødammen and Bjørnholt are neighbourfarms on the south side of Bjørnsjøen (Bear Lake) while Bonna is a farm on the north side of the same lake. Today all of these farm are in the middle of nowhere and they are not driven as farms anymore.
Gina Kaspersdatter's first marriage with Halvor Olsen (or Nilsen, his father was Oluf Nilsen) October 6th 1917 in Vestre Aker Church. Marriage no. 41 on page 85 in the Churchbook of Vestre Aker, no. 15, 1904 - 1929: https://www.digitalarkivet.no/kb10040903240093
Gina Kaspersdatter's second marriage with Birger Gustavsen June 24th 1922 in Vestre Aker Church. Marriage no. 38 on page 132 in the same churchbook as above: https://www.digitalarkivet.no/kb10040903240140
Bonna: https://lokalhistoriewiki.no/wiki/Bonna_(Nordmarka)
Bjørnholt: https://no.wikipedia.org/wiki/Bj%C3%B8rnholt_(Nordmarka) It's Birgers daughter's daughter that runs Bjørnholt today.
So, Mike, you should tell the person that emailed you that he/she mixed the two Ginas on Geni. What is linked on Geni is correct according to the primary sources. There is lacking a good deal of the facts I have found and I can add them if you want me to, allthough I have no relationship to these persons. There is also a waiting merge on Gina Karoline Mikkelsen
