You’re right. Reporters didn’t kill Diana, but they certainly did contribute to the accident that took her life.
You might include it somewhere on a list, but it'd pale in significance to these items:
* No one in the car was wearing a seatbelt
* The driver was intoxicated
* The driver was exceeding the posted speed limit by a comfortable margin.
There might be a place for "not wanting to have your picture taken" somewhere near the bottom of the list.