u can't
of course no when you chat with a friend they have no idea what you are saying. That is why they call it "private Chat"
Go on their homepage then the lower part of the picture and says block friend (or delete friend) MUST WORK
Don't worry, all you have to do is click on account the last from home. Then you click on account then click edit friends.
On the top right side of the home page, you can see the tab Account click it. Then find the edit friends tab on it. It is usually the first one. Once it's fully loaded, find the friend you want to...