Convention or not, to be still mourning for a dead spouse is a great and effective excuse for fending off unwanted attentions- I speak from experience here. For reasons which I'd rather not go into in Pemberley, widowhood, like divorcehood, seems to attract the most unreasonable, lascivious and unwarranted overtures from all directions! The only "polite" countering to these that actually worked, in my experience, was to be "in mourning".