so a friend of mine hyphenates her last name so its: maiden-marriedname.
how do I address a christmas card to her and her husband?
Just a guess, but I'd say:
Mr. Hisname Marriedname and Mrs. Hername Maiden-Marriedname
(I know that, historically, Mrs. Hername Marriedname was used for widows, I beliive restrictions on that have loosened