Officers' Ladies refers to the wives and daughters of the officers of the company. 

The following is an excerpt from a work-in-progress:

    The wife or daughter of an officer was a middling or upper class woman , considered to be a lady, through her economic and social standing.  In addition, she would have been educated, most likely having attended a female academy where she learned needle arts (including embroidery, tambour work, drawing, and painting), domestic arts (sewing, cooking, knitting, marking or putting initials on clothing, etc.), and an education in the subjects of composition, geography, history, math, natural and moral philosophies, to name a few.   She might also have attend a dancing academy to learn to dance, which would also enhance her posture and deportment. 
        Many officers chose to take their wives and families with them to the westward country (which included the Old Northwest, that include Ohio, Indiana, Illinois, and the Louisiana Territories, such as Missouri) or to the southern territories (Georgia, Alabama, Mississippi, and Tennessee as well as the southern half of Louisiana).   These isolated places posed hardships for raising a family as well as having some sense of a social life, but having a family near was a boon for an officer ,who would otherwise face loneliness or be drawn into taking on a mixed blood or a Native American woman for companionship even though these illicit relationships were forbidden by military regulations. 
        For the wife who accompanied her husband westward, she would face the loneliness of female companionship.  Officers wives did not generally associate with the wives of common soldiers.  There was an invisible social wall between them.  So creating a society of the officers' ladies was an important part of garrison life.  Sometimes, fellow officers threw-in their rations for a noon dinners or for a nice supper meal where they all could share letters from home, news from newspapers, and the happenings of the fort.  Occasionally, there might be a dance for the officers and ladies.  The Fourth of July was the most major holiday observed by all.  This would be followed by a thanks giving meal in the fall after the harvest was in, and Christmas, depending on the religious background of the commanding officer. If the officer happened to be a Congregationalist from New England, he and his family would not observe the holiday.  In areas where the French were prominent, New Year's Eve would also be observed.
        The officers' wives and daughters  spent their days working on sewing for themselves, their children, and infants, from undergarments to dresses and clothing for husbands from cravats to shirts to drawers; knitting; writing letters back home to family, to other officers' wives at other forts if they knew any;  keeping a diary or journal; and reading, particularly novels and history.  Recreational activities might include taking walks, collecting wild  flowers, and horseback riding (side saddle, of course).  They may have even taken on the task of light gardening as often officers had extensive vegetable gardens, and these may have also included some flowers and herbs. Generally, they might perform light housekeeping, but may have had a slave or hired a local mixed-blood woman to clean, even cook.  If the officer wished, he might have a man's servant or waiter from the ranks who would do the cooking. 

Recommended clothing guidelines:
An officer's wife should be dressed in tailored clothing, not loose short gowns and high waist petticoats.  DO NOT use any polyester for any period gown or undergarments.

Chemises: A lady's wardrobe should consist of two - three white lightweight cotton or fine linen chemises which the neckline shape to reflect the various necklines of dresses - one might be squared, another rounded, and a third low in the back and front.  Overall, the cut of chemises in the front should come to about the top of the nipple line if one were wearing a stay.  A chemise is your underwear.  A lady would normally have up to seven to ten of these.
Stay: most middling class women owned at least two stays.  Again, the period correct look is to have the tops of the cups of the stay meet at mid-nipple level.
Morning Gown: A morning gown is what you wear when you first get up and before you receive any visitors.  it is informal clothing - however, there is nothing informal about a morning ensemble.  It should consist of a robe or short jacket with a high collar and long sleeves and a high waist petticoat, usually in white muslin. Fashion prints from both London and Paris reveal that these garments were often trimmed out in lace, ruffles, and/or pin tucks.Sometimes, it could be a a jacket made-up in a print. Worn with a frilly day cap.
Under Petticoat: an everyday petticoat with two or three tucks around the hem as well as a fancier petticoat with ruffles around the hem should be considered.  The basic under petticoat could be made up in cotton muslin.  The fancier petticoat could be in silk.  Even more to consider is to make colored bodice petticoats to wear under sheer gowns --like peach or mint green or powder blue or pink.  This item would be worn over the stay. and chemise.
Stockings: white cotton is the most recommended.  There are now sutlers that have silk stockings available.
Dresses: have at last two dresses  for a weekend event.  These dresses should be carefully fitted to your body.  Suggested styles include front opening, as in apron front or bibb front;  back closing (ties, hooks & eyes, buttoned, or laced up); and a robe style, sometimes known as a cross-over gown (it closes on one side under the bust).  Suggested fabrics vary depending on the purpose of the gown -- a white or buff white gown was the rage and usually worn out for dances, celebrations, soirees, even promenades.  Otherwise, if you want a printed gown, be on the lookout for period prints (often from quilt shops -- but avoid anything that is a toile or furniture fabrics).  Silk fabrics, cotton voile, cotton lawn, cotton batiste, worsted wool, are all suggested.
Ball gown:  You should consider having at least one ball gown, depending on your husband's rank.  Women frequently remade gowns to make them look like a new style.  Buy silk - taffeta, china silk has a nice flow to it, changeable silks; silk organdy, silk gauze, or silk net for trimming it out.
Cape:  A nice silk cape with a hood is a nice way to arrive at a ball.  This would not be a cloak.  It is a shorter garment.
Pelisse:  This is liken to a coat but shorter, usually 3/4 length.  Most commonly made from silk.
Riding habit:  Not all ladies road horses, but if you wish to present this look, there are patterns out there (rocking Horse and Janet Arnold).  The habit included a jacket, high waist petticoat,  a habit shirt (like a man's shirt but with feminine frills, a cravat, a vest (usually fancy silk brocade), gloves, and a hat to top it off.  Sometimes, women wore men's drawers underneath.
Spencer:  A tailored high waist jacket, the plainer the more in keeping with the time period. Silk, Velvet, wool, wool & silk combination.
Cloak:  Wool cloak - going out of fashion for ladies but useful when it it brutal out -- red, blue, green.
Redingote for a lady:  This would be more like a coat. wool, silk, mix.  Military trimmings were popular.
Shoes:  slippers and bootees were most common.  See Robert Land's selection.
Accessories:  reticules or indispensibles; parasol; tippet and muff; work bag for sewing or knitting; trunks; period swing box; hat box; gloves - short and long; fans; shawls; chemisettes; embroidered neckerchiefs and head scarfs; jewelry; and the list could go on.
Bonnets & Hats: Silk, velvets, and even wool bonnets have shown up in  inventory lists, as items for sale on ebay and other auction sites.  Straw was mainly for warmer months, but not entirely. 
Other head wear: turbans, toque, scarves, are along the most common.