I think there's plenty of blame to go around here. A lot of it has to do with the tabloid press, which is in the business of making money in whatever way it can. If people weren't so very interested in these rumours, the tabloids wouldn't keep on about them. This didn't become an issue until Hewitt started hinting that he and Diana were intimate years before they were supposed to have met in the first place - all that business about being under hypnosis or whatever. It isn't Diana's fault that he didn't keep his mouth shut about that. If he really believed he was Harry's father, there were ways to find out that didn't involve yapping to the tabloids; if he didn't believe it, then he should have held his tongue. The guy apparently was looking for money, and like a lot of people he decided that exploiting Diana was a good way to get some. When someone does that, it isn't fair to give them a free pass and simply blame her.