Find positions that still stimulate her but don't cause as much friction for you. Changing angles can do wonders for lasting a long time. Changing positions can cause her to lose her orgasm, but just by dropping your hips or moving a little you can make things tolerable. I also find varying tempo works, like 1 fast then 9 slow, 2 fast 8 slow and keep going - drives my partners crazy. Constant movement is key though.