Here's why your lady is probably denying for intimacy

Maintaining interest
Just like men like to chase, women like to toy. If she allows you into her bed too soon, you might lose interest in her. That is why, she is playing hard to get.

Commitment
Women often withhold sex when they want their man to commit to them. If you have not given her a clear cut idea about what the future of the relationship is, she is liekly to wait and see if you commit.

Feeling bore
She is bored with you If she is withholding sex for none of the above reasons, then may be she is just bored with you. She might even be looking for greener pastures.