We have no more control over our orgasms than men do. We can't just cum on demand, and if a girl claims that she can, she's faking it in order to make you think you're pleasing her or because she's not in the mood and wants the sex to be done and over with. But realistically, no, we absolutely don't. We can control trying to hold off from cumming, and we can do stuff to try to make ourselves cum quicker, but we have no real control over whether or not we actually have one. Wouldn't that be nice! Would certainly make my sex life a whole lot easier.
Keep in mind that over 80% of women fake their orgasms. While that's a whole other topic of discussion, it may apply here, since it's food for thought about whether or not the girls you're sleeping with are even having orgasms, and given that most of them probably aren't, again, they don't have any control over whether or not they cum at all.
Orgasms are a result of our muscles contracting over and over again, being a release from all the buildup and consistent friction. It's not something you can control with your mind, it requires a certain physical stimulation to happen. So unless you're providing that exact stimulation that a woman needs to reach orgasm, it's not going to happen.