Ray Batchelor writes: 1913 newsreel footage from Journal Gaumont of Lucile’s mannequins tango-ing in a fashion show as the clients drink tea. Scanned from the book “The Mechanical Smile” by Caroline Evans.
https://www.pinterest.com/pin/525443481495682140/

According to the Victoria & Albert Museum website, “Lucile is often credited as the first fashion designer to use professional models, and she started the tradition of using catwalk shows to show case her work. These would be invitation only tea time presentations, complete with stage lighting, music and programmes.” http://www.vam.ac.uk/__data/assets/pdf_file/0012/250122/lucile_aad-2008-06_20140723.pdf so it is not impossible that the women are dancing to tango music. The Paris premises opened in 1912 at “11. Rue de Penthièvre” http://www.nms.ac.uk/explore/collections-stories/art-and-design/lucile-dress/ information taken from: Lucile Duff Gordon, A Woman of Temperament, (London, 2012). Originally published as Discretions and Indiscretions by Lady Duff Gordon (London, 1932)

Interestingly, according to the narrator of this short film promoting a museum exhibition in 2008, Lucile designed dresses for Irene Castle, half the famous ballroom dancing couple Vernon & Irene Castle. The video shows an apparently tight skirt with a highly practical vent which allowed full movement: https://youtu.be/OTgXjqEuRR8

“Presentations to the specially invited audience must have been splendid. Lucile had a stage built so that women could preview the clothes in comfort, and she installed curtains and scenery for added drama. She trained models in deportment and style, and paid them, so that they could do credit to her clothes. Thus the catwalk show, complete with beautiful walking mannequins, was born. Her style shows specialised in tea-time presentations, palm fronds, music from a string quartet and professionally printed programmes.” – http://melbourneblogger.blogspot.co.uk/2010/04/lucile-duff-gordon-couturier.html

[12 01 2020] I have since written about this and related images:

“Tango teas, trousers and autonomy: images of women dancing with each other in the early 20^th century” given at POP Moves Conference, Im/mediate bodies: Materiality and mediation in popular culture, 15 October 2016 https://www.researchgate.net/publication/312300839_Tango_teas_trousers_and_autonomy_images_of_women_dancing_with_each_other_in_the_early_20th_century