What is the proper way for a gentleman to refer to a female friend who is the fiancee and then later wife of his closest male friend (i.e., how should Holmes address Watson's fiancee-then-wife, Mary) (this is talking to her directly, in a private home, which I can't recall really happening in the books) and vice-versa, how should she refer to him in the same setting? Would he always be expected to address her formally (and does the marriage itself change anything in terms of what's acceptable?) and would the same expectations be had of her when she addresses him? (Of course I can handwave bits of this due to the situation they end up in not being remotely 'proper', but I'd like to know the rules before I break them).
Terms searched: Victorian forms of address, Victorian terms of address, Victorian etiquette and replacing Victorian with 1880s/1890s also but nothing specific is showing up so far for ordinary people (as opposed to titled people) or for women who are already engaged/married.