Don't go straight with rubbing her clitoris right away, you have to do what we have discuss in previous post, foreplay. Yes, you have to start the whole thing from foreplay, it's important to turn her on before you start. We have show you the way to play with her clitoris, just massage her clitoris with circular motion, you may get the lube from her vagina to make her feel more comfortable.
Once you make her so high that she wants you to penetrate her, put your middle finger in her vagina. Middle finger is good for you to go in and out faster, but you have to put yourself in a good position, spread her leg wide open and sit in between them. If you are able to rub her clitoris with one hand and play with her vagina with another hand, this is the best. She have higher chance for the orgasm. There is a good way for you to hit her g spot, just use your middle finger, palm face up and try to hit her g spot and vagina upper part with it. Go slow and see how she react to it.
You may ask her to masturbate in front of you. Female masturbation is a good way that leads to orgasm, you may learn some trick to give her oral sex during foreplay. Sometimes girls like oral sex and foreplay more than penis penetrate sex, and it may give her the orgasm she wants. In return she will give you a lustful night.