Even if she DOES have solid proof of something she's not a reporter and the only way it's actually "news" is if his affairs affected the State of California. Otherwise it's gossip.
That's a rather limited definition of news, don't you think? Politics and state affairs are not the only things considered news. Especially in this case - as both members of the couple would be considered celebrities.
Does Arnold's affair and child with the housekeeper affect the state of California? I don't think so, but I see a lot of news coverage anyway. Are you saying that is also not news?
News really is defined by what people want to know, what people will read and watch. Of course, it is nice or morality driven to say peoples' personal lives as news is "gossip" but when they are famous, it becomes news.