Ideally, she wouldn’t have to ask because a HVM would want to pin down a woman he values. But if for some reason he doesn’t initiate, she can say something like, “I know we haven’t really discussed this before, but i want to make sure we’re on the same page before taking this any further. I need to know that we are sexually exclusive.”

With that being said, FDS preaches that exclusivity is kind of a null label unless you also have the label of girlfriend. This might not entirely be in line with what she wants right now if her life is too busy for a boyfriend, but she should at the very least express the need for sexual exclusivity, if only for health and emotional protection.