(NOTE: this question reveals both the plot-details of the film's ending and the film's major twist.)
In the climax of Paul Verhoeven's Elle (2016), all the characters are at a party. Elle leaves the party with Patrick, telling Vincent as she leaves that Patrick will take her home. On the ride home, she provokes Patrick by telling him she'll go to the police and report his previous attacks. Patrick pursues her into her house, once again wearing his ski mask. Elle puts up a better fight than before but is ultimately pinned to the ground again. Vincent comes home, sees Patrick in the act, picks up a log and mortally wounds him. Patrick stands up, asks Elle "why?", and dies.
Elle's actions here seem (to me) fairly intentional, especially her behavior in the car. She seems to want Patrick to follow her into the house and attack her.
Similarly, Patrick seems to think that this was a setup, since he asks her (and not Vincent) "why?". (In any case, asking Vincent would make no sense; obviously he attacked because he saw Patrick raping his mother.)
It could be that this is just another instance of Elle trying to turn Patrick's assault into a semi-consensual relationship, but she doesn't just make herself vulnerable, she makes Patrick angry. And, as previously stated, she fights more vigorously and effectively than previously. However, it does not seem that she was planning on being able to successfully defend herself against Patrick alone, because she doesn't prepare for the fight by fetching the mace or the hatchet.
So, was this planned? Is there something in what Elle said to Vincent while leaving the party that caused him to also leave the party and follow them home?