Here's what theppeerage.com says:
" Paul Friedrich Herzog von Mecklenburg-Schwerin was born on 12 May 1882 at Schwerin, Mecklenburg-Vorpommern, Germany.1 He was the son of Paul Friedrich Herzog von Mecklenburg-Schwerin and Marie Prinzessin zu Windisch-Grätz. He married Sophie Viktoria Ornig, daughter of Heinrich Ornig and Countess Fjodora Aleksandrovna Tolstoy, in 1900. He died on 21 May 1904 at age 22 at Kiel, Schleswig-Holstein, Germany.
Paul Friedrich Herzog von Mecklenburg-Schwerin gained the title of Herzog von Mecklenburg-Schwerin.
Children of Paul Friedrich Herzog von Mecklenburg-Schwerin and Sophie Viktoria Ornig
Elizabeth Herzogin von Mecklenburg-Schwerin b. 19002
Gisela Herzogin von Mecklenburg-Schwerin+ b. 19012 "
However, it seems they took their info from "Alex Leiß Auersperg, "re: von Mecklenburg-Schwerin Family," e-mail message from unknown author e-mail (unknown address) to Darryl Roger Lundy, 5 October 2008. Hereinafter cited as "re: von Mecklenburg-Schwerin Family". "
No info is listed on the online gotha and that era of dress doesn't strike me as a 1900 wedding dress.