See the reason it's hard for me to find a female lead for this is because you need someone who can act humble, act like they have low self esteem and act like they really are a sweet person underneath th hooker job!  The problem with a lot of starlets now-a-days is that they are really confident and a lot of movies portray these women being super confident and in charge (which is a great thing for society to see - but not great for this type of movie)