I originally had Marguierite de Bourbon as wife of Guillaume; and Turton states that she is Beatrice (no last name); some on World Connect name her Beatrice de Beziers; still others name her Adelaide de Beziers; but I am following a Frenchman? named Pablo Mera Gadea, who names her Adelaide Trencavel. She is probably the same person referred to as Adelaide de Beziers, as Adelaide's father was Raimond Trencavel, Viscount of Carcassonne, RasEs, BEziers, Agde, & Albi.
Note that, according to a posting to SGM by Nathaniel Taylor, Adelaide Trencavel possibly m. Sicard Viscount of Lautrec, and she had a sister Beatrice who possibly m. Raimond VI Count of Toulouse. Thus maybe it was her sister Beatrice Trencavel that married Raimond, instead of Adelaide. But, like I said, I am following Pablo Mera Gadea's pedigree.