This looks beautifully drawn so far, I am almost inclined to say stop here and let us imagine the rest. the eyes and lips are well done. And you have done a wonderful job on the highlights. It looks like you are using watercolors I usually use oils but i am feeling motivated to try my hand at some watercolors. Excellent work! Seriously consider stopping here and just use some clouds or just fade it in I think if you go further it may take away the allure.
Wonderful! As a rabid Marilyn fan I can say with her its all about the eyes and the smile, and you have captured the truth behind both of those Excellent!
You must be the modern day expert on drawing and painting the fabulous MM.
Who better to sculpt her?