It started with 2 quick (5 minutes) drawings of the model, making sure to overlap them. Then choosing lines and shape to bring to attention, using watercolour pencil.
I found this paper with a bit of a Biba look to it and added that, then block coloured the purple with gouache, I think.
It still looked incomplete, so using pencil I echoed the shapes of flowers in white, then in purple to achieve another link.