The Way Mary Dresses for a Wedding

i just watched the episode when Lou's ex wife Edie gets remarried. Mary attends the wedding with Lou to give him moral support.

Mary is wearing a white dress. It's considered ill form for women guests to wear white to a wedding. Edie wore light blue and Mary wore white. I wonder why a woman like Mary who was always so proper would overlook that bit of etiquette?

Mary is also wearing a white pants outfit when Georgette and Ted get married in her apartment. True it was a spur of the moment wedding. But I find it interesting that Mary wears white to other women's weddings! At least she wore pale yellow to Rhoda's wedding.