I cannot beleive that Vilhelmina was baptized 40 years later her burth. I think that the version about Jewish connection is possible. May be she needed some documents to prove her non-Jewish confession. So, to find her burth certificate I recommend you to appeal to the Central State Historical Archive of St. Petersburg. Postal àddress: ul. Pskovskaia, 18 190121, St. Petersburg E-mail: firstname.lastname@example.org http://spb.rusarchives.ru/Central_Sta…http://spb.rusarchives.ru/Central_Sta…;http://www.rusarchives.ru/state/cgiaspb/http://www.rusarchives.ru/state/cgiaspb/
But I would like to warn you that this archive is very slow. You may wait some months for their reply.