Heh. I am more or less like your girl. I would say don't be afraid to pause or bring hands or toys into it to get her off faster. Also changing positions is a great way to stop, pause and change the flow. Usually I'll ride a guy for a while--doing this allows me control and lets me go slowly, building it up a bit. Then we'll finish with really hard, fast doggie style. You might try doing a position where you control the tempo and finishing with doggie style.
If she likes it doggie it's probably because of g-spot stimulation, so you might try manually stimulating her g-spot beforehand. Another position you might try is reverse cowgirl...great for g-spot.
Another thing--if a girl tells you she doesn't mind not coming...that's okay. Don't worry about it. I've had a hard time in the past with partners because it doesn't seem like I come...I have several small orgasms that add up to what one big one would be. So if she's okay having sex without coming, you should be okay with it too. Orgasms during intercourse are like a bonus. Try giving her one some other way--be it manual stimulation, oral, whatever. Women can experience intense pleasure through sexual intercourse without having an orgasm.
Hope that helps.