I don't have any references handy, but I always thought that mademoiselle+ was abbreviated +Mlle -- upper-case M, no period.
However, in looking through an early version of Tolstoy's "War and Peace," whole paragraphs of which are in French, I see the French companion of Princess Marya Bolkonskaya referred to as m-lle Bourienne.
Was that hyphen a correct usage in Tolstoy's time?
Relax NA! You are retired – you don't have to worry about these things any more.
???
I doubt very much that "worrying" about 19th century abbreviation conventions was ever part of NA's job description.
However, I'm not quite clear OP: does your question pertain to a Russian or an English version of Tolstoy? I don't have my copy of Война и Мир to hand, but "m-lle" doesn't look at all odd to me. This may be because I've only read the book in Russian and that's the way it usually appears in the Russian (see here or here, for example).
Googling around, I only see it in a Russian source (but published in Paris in 1896), Correspondance de Sa Majesté l'Impératrice Marie Fédorowna avec Mademoiselle de Nélidoff, suivie des letters de m-lle . . . (Amazon won't tell me m-lle who).
I do see a number of 19th-century uses of "m'lle" though.
Edited by: Princesse Troubetzkoy
Thanks, all, for your contributions; they have helped me to relax.
Myanmarbound: After working as an editor for 30 years or so, I found myself "worrying" about all kinds of things I saw in print. Retired now, I still feel that I should find out if a text reflects conventions of the time or is simply wrong.
zashibis: It was a Russian text; it may have been the same one as the first of your two links.
VinnyD: I'm "worried" by that z in your editor's surname; I would have used an s.
So would I, NA. But I half-rememberred the French spelling of the editor of the volume of letters I mentioned: Publiée Par La Princesse Lise Troubetzkoï.
zashibis -- it's surprising what you can end up worrying about as an editor. You wouldn't have thought that many years ago when I was subbing (copy editing) at a woman's fashion magazine that I would have to know when it was appropriate to use Romanov or Romanoff but there you go.
One thing I am looking forward to when I stop editing is not waking up in the middle of the night wondering if I have misplaced a comma.