Debra's and Mary's question about the addition of the Queen to the card pack (the "why" part at least) is really a very interesting one. It's one of those areas of playing card history where informed speculation is fun, desirable, and actually necessary, since there is nothing written on this specific question (that I know of), and it seems to indicate something broader about European culture.
Only European cards have her, and then only some kinds of European cards. The Mamluk cards - the structure of which is presumed to be the immediate ancestor of European cards - have only a King with two lieutenants.
In playing cards there is also the phenomenon where the Jacks, Valets or Unters - usually two of them - are portrayed as women. I don't think there are any current kinds of playing cards with female Jacks (I could easily be mistaken), but they are observable now and again in historical cards (The most extreme example is the Cary Yale Tarot, which has female knights and valets in each suit, so that the sexes are exactly balanced).
The latter question seems easily answerable: Jacks are typically portayed as youths, where the sex appears indeterminate, so occaisionally a card designer will make the sex differences clear through physical attributes and clothing.
The Queen, on the other hand, is an addition to the pack, not implicit in the ambiguity of depictions of Kings, and so not the reification of implicit ambiguity, unlike what appears to be the case for female Jacks. Cards either have a set of Queens, or don't (I'm also not aware of any packs with two Kings with his ministers and two Queens with hers).
John of Rheinfelden already knows Queens in some kinds of German packs in 1377. Bernardino of Siena mentions them in a sermon given in Siena in 1424, along with Kings and higher and lower soldiers (like the Ober and Unter of German packs, and the Knight and Valet of Tarots). Bernardino never mentions the trumps, so it appears that he is describing what would be for his listeners the standard kind of playing cards, including four court cards (not called "courts", but "figures", to distinguish them from the figure-less number cards). Therefore there was, for a time, a standard 56-card pack in Italy. It lasted long enough to become the same pack and number of court cards used when the trumps were added to invent Tarot.
My answer for "why?" the Queen was added to playing cards is that it reflects European society, where women have always played a much more public role than in Moslem society. In fact women were completely effaced from public life in Moslem society, so that they didn't think "A King with his Queen", but "A King with his ministers", when they thought about the top level of society. The "King" in Moslem society has consorts, not a Queen, and they are never seen in a public capacity anyway. In European society, by contrast, a King must have a Queen, and she always appears with him in public, and is quite frequently the ruler in her own right. The higher status and power of women in European society is indigenous, despite the patriarchalism of Greek and Roman society, which was superficial compared to Moslem society (and others).
So, the original cards' "King with his ministers" suggested a court to European cardmakers, when they came to put images on the highest cards, and to a European, a King's court cannot be complete without a Queen.
A real, living court simultaneously suggests romance, intrigue, and instantly makes playing cards a metaphor for society. The same thing happened to the Chess pieces, when the original, Eastern vizier, the King's counsellor, was transformed in Europe instead into his consort, his Queen (already by the 10th century). It seems that the European imagination - at least in France and in parts of Germany and Italy - can hardly imagine a story (which a game is) where a King does not have a Queen. It is a kind of "ludic logic", where the story forms around the name or image, and then takes on a life of its own.
However, her fortune in the 56-card pack and in playing cards is sporadic. The national patterns of playing cards in Italy and Spain (the "Latin suited packs") removed the Queen (or never had her, like perhaps in Spain) and have three males, King, Knight and Valet. In Italy, only in Tarot packs do the four court cards, including the Queen, survive.
By contrast, in France the Queen was saved and the Knight kicked out. It was French cards that were adopted into a standard pattern in England, so that by the influence of the British Empire, the most common cards in the world today have a King, Queen and Jack.
