Her widower told the MailOnline she died “peacefully after a long battle with chordoma, a rare spinal cancer, leaving two sons aged nine and seven”.
The book claims the singer visited her often before his death in 1991.
It is alleged Freddie’s bandmates and long-term partner Mary Austin knew of the child.
In the book, B said: “Freddie Mercury was and is my father. We had a very close and loving relationship from the moment I was born and throughout the final 15 years of his life.
“He adored me and was devoted to me.
“The circumstances of my birth may seem, by most people’s standards, unusual and even outrageous. That should come as no surprise.
“It never detracted from his commitment to love and look after me. He cherished me like a treasured possession.”
Speaking about B’s claims, Ms Jones writes: “My instinct was to doubt everything, but I am absolutely sure she is not a fantasist.
“No one could have faked all this. Why would she have worked with me for three-and-a half years, never demanding anything?
“In my experience of fantasists, and I’ve met a few, they seek instant gratification, publicity and reward. She has never asked for money. She does not want recognition.
“Both Freddie and her stepfather left her extremely wealthy. She was not provided for through Freddie’s will, but by a private, legal arrangement, so no one will find her mentioned there.”