Can a character develop a life of its own?

A week or so ago author Diana Gabaldon posted a message on facebook correcting reviews of the latest Outlander TV episode about the sexuality of her villain Black Jack Randall. Diana said that he is a not a homosexual he is in fact an equal opportunity sadist who will take either men or women it all depends on who he has more access too and considering the time period the books are set in the reason he targets men more is because women did not usually roam the countryside by themselves. I admit I was confused when she said he was not a homosexual because he does come across that way and claiming that he is not frankly makes things a little confusing. His obsession with Jamie is a little too strong for him to not have some homosexual tendencies. I know that people can fall on a spectrum when its comes to sexuality and I'm not one of those people that thinks bisexuality that does not exist, however, Jack does not come across as a man that likes both men and women. He comes across as a man deeply, disturbingly obsessed with Jamie. There is also the scene when he tries to rape Jamie's sister Jenny and cannot get it up. Jenny laughs at him for his inability to perform. Most people interpret this scene as Jack is homosexual and cannot perform because he prefers men. Maybe. It could be that he has trouble getting an erection or maybe it was her laughter that turned him off. Whatever Diana's intentions were for the character either she did not do a good enough job getting those ideas of hers across to the reader or, more likely, Jack developed a life of his own and went off in his own direction. She might not have intended for him to be homosexual but that IS how he comes across. This brings up an interesting question about writers and their characters and who is in charge of whom. Should we listen to Diana? or should Diana look at her character and accept that he has developed in a way that she did not intend?