sounds like my boyfriend and I....
we've now been together for 11 months and are wonderfully happy. He was my first, and I had never gotten off til I met him.
Just be paitent with her. Talk a lot- ask her what she's feeling, if sex intimidates her, what she does and doesn't like... make sure she's comfortable with everything. Let her know that it's normal to have problems getting off, especially at first. It took me 8 months. Give her time. She'll come around (so to speak)