Gleeson White wrote, "With a delightfully innocent air these two sisters disclaim any attempt to acknowledge that Egyptian decoration has interested them specially. 'We have no basis.' Nor do they advance any theory." The beginning of her artistic career reflects broad strokes of experimentation. Largely drawing from her imagination, she reinterpreted traditional themes, allegories, and symbols in inventive ways. For instance, immediately following the 1896 opening of her Glasgow studio with her sister, she transformed broad ideas such as "Time" and "Summer" into highly stylized human forms. Many of her works incorporate muted natural tones, elongated nude human forms, and a subtle interplay between geometric and natural motifs. Above all, her designs demonstrated a type of originality that distinguishes her from other artists of her time. Mackintosh's most popular works include the gesso panels "The May Queen", which was made to partner her panel "The Wassail" for Miss Cranston's Ingram Street Tearooms, and "Oh ye, all ye that walk in Willowwood", which formed part of the decorative scheme for the Room de Luxe in the Willow Tearooms. All three of these are now on display in the Kelvingrove Museum in Glasgow. The 2017-18 restoration of The Willow Tearooms building has seen a recreation of ""Oh ye, all ye that walk in Willowwood"" installed in the original location within the Room de Luxe. Her grandest work is the "Seven Princesses", three wall-sized gesso panels showing a scene from a play by the same name, by Maurice Maeterlinck. This work was extremely popular in Vienna and its surrounding art scene. When the Waerndorfer villa was sold in 1916, it disappeared from public view for a long time. In 1990, it was rediscovered in a crate in the basement of the Museum of Applied Arts in Vienna, and is now on permanent display in the MAK. In 2008 her 1902 work "The Red Rose and the White Rose" was auctioned for 1.7 million UK pounds or $3.3 million.