Everybody seems to love Rachel. She is a harlot, a temptress, trouble in a skirt, and irresistible to Ryan. She is the living embodiment of the drugs he dishes out. He knows she is bad for him, he knows that continued consumption will only end in disaster, yet he is unable to resist her pull. Mark has her measure. As someone who has not had the misfortune to fall under her spell, he can see right through her, and tells Ryan as much: "That girl is just wrong mate, she can play you like a violin."
So far Rachel has received nothing but favourable comments from the readership of White City, even the female readers. Despite her shortcomings as marriage material, and the fact that in real life you probably wouldn't touch her with a bargepole, she is a livewire who has 'good time' written all over her. And when it comes to characters in a book, she is exactly what makes life exciting.
As with all the characters in White City, Rachel is based on no single person, but rather on the worst bits of a lot of girls I have known over the years. Some of her moments are completely fictional while rooted in reality, others skirt dangerously close to what actually happened.
Her character was not planned, which I think is kind of fitting. She came along in my mind as abruptly as she appeared in the book, sitting in Andrew's lounge rolling a joint with a glimmer in her eye. Her fondness for Ryan and their evident chemistry made her the ideal candidate for Ryan's love interest. As things panned out, she became quite a force majeure in her own right, and her character develops accordingly.
It always helps to have someone in mind when developing a character, and all the bad bits of all the girls I've known came together in my imagination as ... Mini Anden. If she could act, I would suggest her for the role in the film.
I hope this doesn't spoil your own mental image of Rachel, whatever state of undress she might be in. I would be interested to learn of any other contenders for the role.