Here's my process in creating this piece. I've said it before but I think its really important to create your own reference images. I always think whats the point of drawing a realistic replica of a photo? It's already been created by that photographer no need to put another version out into the world. You can though pull it apart and turn it into something amazing that no ones seen before and make it your own. 

I kind of make these "Frankenstein" ladies in photoshop to create exactly what I want to draw in my head. So its the body from one image, the head for the another, the hair from another and the flowers are inspired from a tattoo. You can see all of this in the moodboard I created. 

You can see below how rough the reference is I create in Photoshop. It doesn't need to be perfect you can fix up the mistakes in the drawing. It's just a guide line for you to look at while you draw.