She was probably following the trend popular during the Anglo-Boer War in which women showed their patriotism and support of the war by dressing in costume variations of British military uniforms. Sometimes (as depicted in other images in this section) such women chose to be photographed in the actual uniform of a male acquaintance or family member while on other occasions these uniforms were of a clearly theatrical or costume nature.
This is an example of the latter. She wears a small stylized version of the slouch-type hats that were so popularly worn in South Africa. She also wears a costume (non-functional) ammunition bandoleer over her shoulder. One of the more interesting and small details in this image is the intertwined hearts brooch she wears at her neck which is just visible between the closing of her stand a fall collar. This "sweetheart" brooch would indeed seem to indicate that she was related in some way to a member of Her Majesty's forces serving in the then-ongoing war.
Biddle & Dowdall - Photographers
49 King William Street, E.C. & 1 Ondine Road, East Dulwich, S.E., London, England