Am adding an excerpt I just found on Medieval French naming traditions, because I think it might be of interest here. Sorry, it's going to come through as a wadge of data here - I've also put it at the end of my Huguenot Settlers project, where it might be easier to read. http://www.geni.com/projects/SA-French-Huguenot-Settlers/8652
A Note on Medieval French Naming Traditions
"It will strike the modern reader as strange that the lady was styled Mademoiselle after as before her marriage, and the use of the title needs a word in passing. The general use of Madame to designate a married woman dates only from the 17th century and even then it came slowly into use. In earlier days the title was reserved for ladies of a certain rank somewhat as ' Lady ' is used in England. These favoured few were the wives of ' les grands ', of the princes of the blood, semi-sovereign princes, Marshals of France, certain of the highest nobility, and of the chevaliers des ordres ; also the King's daughters and abbesses and prioresses ; all these could claim the title of Madame. For other women, whether noble or bour- geoise, wed or single, Mademoiselle was the only title in use.
But whereas in the case of a bourgeoise the husband's or the father's family name followed the title the noble- woman would almost certainly have made use of a territorial name. Montaigne protested against the habit.
" It is a vile habit and one fraught with evil for France for people to be called after their estates, and one that occasions more confusion of families than any other thing. A cadet of good family, who receives as his portion an estate, whose name he bears with credit, cannot abandon it with honour. Ten years after his death the land passes to a stranger, who in his turn bears the title."
Montaigne felt the loss of the hereditary honour which could cling round a name handed down from generation to generation, but he also felt the confusion which arose from the habit he condemns. Every child, girls as well as boys, might bear a different name and much of the significance of events in history may be lost by those who fail to realize relationships through the maze of names.
In England the eldest son of a peer may bear, by courtesy, some secondary title belonging to his father ; his brothers will use the family surname. In France not only great noblemen, like the Constable Montmorenci, whose five sons were known as Montmorenci, Damville, Montberan, Meru and de Thore, but the sons of every little squire with a small property or two to divide was known by a different name Thus in the Mornay family the eldest son was de Buhy, the second du Plessis Marly the third de Beaunes ; their uncle was d'Aubleville and his son Villarceaux, and so on throughout the whole nobility of France. And furthermore, as Montaigne complains, should the property pass into other hands the name went with it and the nobles saw springing up a new class of rich bourgeois proprietors ' roturiers ' who bought the right to use the name along with the territory to which it belonged . One other point is worth calling attention to. On marriage an Englishwoman loses her maiden name and henceforth in legal signatures as in common parlance uses only her husband's surname. An old traveller in England noticed this as one of the peculiarities of the subjection of a woman to her husband.
" Wives," he says, " are entirely in the power of their husbands, their lives only excepted. Therefore when they marry they give up the surname of their father and take the surnames of their husbands."
In France this is not so. A woman never loses her father's surname and signs with it, at least in all legal documents, after as before marriage. Mile, de Buhy was Madeleine de Bee Crespin till her death, just as du Plessis' wife was Charlotte d'Arbaleste when- ever she signed a letter, in spite of her first marriage to de Feuqueres and her second to du Plessis. http://archive.org/stream/huguenotfamilyin00mornuoft/huguenotfamily...
It is not a problem at all if people stop thinking "rules", - it's quite simple: Just enter what the sources tell you.
Do NOT attempt to fabricate facts like we see too much on for example removing women's own identity by registering them with a married name without any source citation that tells that she had and used one.