b. Chacune des anciennes copines de Marie était si embêtante que, à un moment ou à un autre, elles / *ils se sont disputé(e)s.
Each of-the former girlfriends of Marie was so annoying that, at a point or at another, they-fem./*they-masc.each-other are quarreled
Each of Marie's former girlfriends was so annoying that, at some point or other, they had a fight