Gustav Kobbé,
The Complete Opera Book
“ She knows nothing, however, of the treachery Hagen is plotting, or of the love-potion that has aroused in Siegfried an uncontrollable passion to possess Gutrune, has caused him to forget her, and led him to win her for Gunther. There at Gutrune's side, and about to wed her, stands the man she loves. To Brünnhilde, infuriated with jealousy, her pride wounded to the quick, Siegfried appears simply to have betrayed her to Gunther through infatuation for another woman. ”
