Anne Rule had written stories for detective magazines before she met Ted Bundy. When she got a contract to begin writing a book about the murders of several young women that were thought to be the work of a mass murderer (the concept of “serial killer” had not been invented yet), there were no suspects in the case. The fact that she was a friend of the killer had nothing to do with her getting the contract.
A lot of people think she only got the contract because she knew Bundy. That simply was not the case.