Good advice on this thread. I think Logic nailed it best. It seems like it's more a matter of you coming to terms with your dom-ness than with her submission.

If it pleases her to please you, and you are only worried about pleasing her, then you reach a stand-off. Take control, and tell her what you want, even if that means she has to delay gratification (especially if that means she has to delay gratification). Even if it means that sometimes you're taking what you want rather than giving what she wants. (If you're both really d/s, those will come hand in hand--so to speak)

And it's not like you're talking about tying her or hurting her without permission, just making her put off cumming. When it comes to orgasm control, the ends always justify the means. There is nothing better than an orgasm you have to work for.