It is always possible to tell if someone is a lady, regardless of what they are wearing. A lady is unfailingly polite and considerate. Manners and morals are the mark of a true lady, not her dress, and certainly not her dedication to fashion.
Nevertheless, a lady will always endeavour to be appropriately attired. By dressing correctly, she shows her respect for others and the situation at hand. She would not go to a wedding in her riding clothes, and she would not go to go shopping in a ball gown.
At a basic level, she shows her taste and decorum by dressing quietly. She does not seek to draw attention to herself through her dress. Elegance is found in understatement. A lady’s apparel should be neat and tidy. It should be made up well and fit perfectly. A lady is neither messy nor slovenly, and this should be reflected in her choice of clothes. As well as this, a lady should consider colour as a matter of importance. A lady should hold fabric to her skin, and see how it compliments (or, indeed, doesn’t compliment) her complexion. While your dress may look perfect when held up by the maid, if the colour drains your skin and makes you look sick, it is hardly fit for purpose.
This consideration should also extend to accessories. Before even adding a ribbon to her hair, a lady should think about how it will look with the rest of her outfit. Gloves should always be a shade lighter than the dress, and like the dress, should fit perfectly. Also, if you are wearing a less-than costly dress, do not wear something else very expensive alongside it, and vice versa. The two items will clash terribly.
On that note, another mark of a lady is good sense. A true lady will not exceed her income on her clothes. A cheaper fabric worn with comfort and ease will convey a more ladylike air, than silks and velvets which leave a lady fretting and fussing after their safety and condition.
In short, a lady should exercise as much discretion in her apparel, as she does in all the other aspects of her life. A lady is known by her good taste and good sense. She shows this in her clothing. Yet, should circumstances be such that a lady ever finds herself wearing the wrong dress for an outing, that her bonnet strings broke and the offending item was lost en route, that she put on her sister’s shoes and is left limping during a walk, her ladylike nature will not be compromised. How she responds to these trials – with decorum and good humour – will show that she is a true lady on the inside, and not one for show on the outside.
 Hartley, Florence, The Ladies’ Book of Etiquette and Manual of Politeness, (London: Hesperus Press, 2014), [First published 1860], p. 21.
 Ibid., p. 23.
 A Lady, Beauty, What it is and how to Retain it, (London: British Library Publishing, 2012), [First published, London: Frederick Warne and Co., 1873], p. 103.
 Ibid., p. 105.
 Ibid., p. 113.
 Hartley, The Ladies’ Book of Etiquette, p. 22.
A Lady, Beauty, What it is and how to Retain it, (London: British Library Publishing, 2012), [First published, London: Frederick Warne and Co., 1873].
Hartley, Florence, The Ladies’ Book of Etiquette and Manual of Politeness, (London: Hesperus Press, 2014), [First published 1860].