Does anyone know how someone can get my name and profile picture from my facebook account?

While playing yo ville on facebook, I had the misfortune of running into a nasty player that was trying to pick fights with everyone. When she ed in on my conversation with another player and rudely demanded to know what I was talking about, I told her I was not talking to her. She then threatened to hack my account and within seconds posted my real name and commented on what my profile picture looked like so I know she had actually viewed it. Anyone know how this is done and what can be done to stop it? Thanks to all who help!