Siddall's works, combining sketches, collage and embroidery, often draw their subjects from myths and fairy tales. Forbidden love, beauty, beasts, transformation and impossible tasks play out on the rich, textured stages of finely worked fabrics. Siddall's particular interest in human-animal metamorphosis and mythical hybrids can be seen in the array of creatures that fly, recline, stalk and prowl across her surfaces: cats, owls, birdwomen with jewel-bright feathers, a flamingo queen, goats and rabbits with human faces and a patient being in an elaborate jacket with a human torso and the head of a donkey.

However, as Lynda Johnson notes, Siddall is also engaged in feminist revisions of these magical tales. If needlework and fairy tales are both crafts that are traditionally associated with women, Siddall employs the one to examine, subvert and reimagine the roles of women in the other, creating female figures who are strange, proud and powerful, beautiful but unyielding.