We know that it's hard not to gossip ever. A lot of the time, it's harmless. But there are also those many times when it's not fair and can be harmful. Again, having someone like this around you pulls you in to their way of thinking. You begin to ignore what's important and taking care of your own life in favor of paying too much attention to the lives of those around you.
For the most part, you're speculating and end up talking trash about someone, becoming one of those judgmental people people don't like. It's best to pull yourself away from people like that and concentrate on your own life and what makes you happy.