The Andrea Pin Up series are nice but are only 80mm scale. Phoenix Phollies is another, but again too small for the OP request.
I can't point out a specific product that will meet your exact needs, but can suggest a few sites with figures. With a little work on your part and depending on the style of figure, you will either have to dress them down or up as the case may be.
There are 95 items listed here in the female 1/6 scale category:
http://legendshobbies.com/catalog/index.php/cPath/24
There is also fantasy figures, but those will likely involve some carving to get what you want. Maybe try http://www.monstersinmotion.com/
A decent one from Solarwind Productions: http://www.foxfirestudio.com/liza.htm
Now you mention she must look American. E2046.com is a great site but is very high on the anime look. I do remember seeing some "adult" rated figures that do look more western, but also exagerated body proportions. Scale is 1/5.5 (yea they have really long legs) but you can decide yourself. At this scale using actual jean cloth would probably not look too bad. You can also putty and sand to create clothing since it just contours the body.
Yea, do not click these if under 18!!!
http://www.e2046.com/product/13620 Angelica
http://www.e2046.com/product/12594 Elsa
http://www.e2046.com/product/14236 Erika
regards,
Jack