I don’t think Nigella Lawson hates Gordon Ramsay, but who really knows? If they dislike each other, I suspect any public “feud” is fueled by journalists and others to help promote cooking shows. In other words, any animosity between the two is just a publicity stunt.
Ramsay reportedly said about Nigella, “Every chef in the country would love her in the kitchen, but we’d never get any work done. She’s sex on legs.” If I were Nigella I would be a little bit angry about this but as far as I know, she didn’t publicly respond to the comment.