If she is willing to have sex, then don't regress back into building attraction. That is an intermediate step. You have I am assuming passed that step if she is willing to shag. Obviously she is experiencing resistance of some sort to sleeping with you.
Build more comfort with her and
escalate the touch with her to an intimate level like
Caressing her face
Having her smell the cologne on your neck and asking her to guess what brand it is
You can also run your hands through her hair.
Notice how i am telling you to escalate the touch with her around her very personal comfort zone which is her facial region.
If she doesn't resist to this, then she is comfortable with you physically however if she is still hesitatant about crossing that line into sexual touch then you need to
build more comfort with her
and also gradually escalate your touch from intimate to sexual.
Try some foreplay as it gets a girl all hot and bothered.
Take it away at least twice as that will amp up her desire for it even more so the next time and you can take that as an opening to seal the deal.
McMaax
http://www.maaximumseduction.com