Most women are understanding if the first time doesn't go the way you'd hoped. Having sex with a new person is always both exciting and nerve wracking. Discovering each other's likes and dislikes can take some time. I agree with smarta$$ that you should try and give her more pleasure, even if you orgasm quickly. You can still go down on her afterward, or what would be better, would be to start with more foreplay at the top of the sex session, so that both of you come out of it feeling satisfied.
"Caring is not an advantage."