Women do often have "rape" fantasies, but you're right that it's very different from actual rape. In their fantasy, the woman has already given consent for a man that she is also attracted to to be overwhelmed with lust. In reality, that has little to do with what is going on during a rape.

The Most Sexually Confident Women Have the Most Rape Fantasies

“It’s important to note that in the way people tended to describe these fantasies, they made it clear that it was consensual, saying things such as “I secretly want it.” Thus, it is not the case that these folks are actually fantasizing about sexual assault — rather, they’re picturing a scenario that unfolds on their own terms, which means the sex isn’t truly forced.”