I'm looking for someone to create the type of female character who willingly puts herself in path of a rapist.
Some ideas for you to expand upon:
She's a police officer who strikes out on her own to catch a rapist but she doesn't intend to arrest him. She wants to be his next victim.
She's a lonely wife and decides to fulfill a rape fantasy that she could never tell her husband about, but ends up meeting someone close to her husband in the process. Who the rapist is can be something you decide.
She knows a neighbor or co-worker is capable of rape and decides to put herself out there to see if he will take the bait. Perhaps reverse blackmail so he has no choice but to rape her.