If you want to remove a user from your friends list, you must first find them through Menu > Friends, by their username or Facebook name. Once you select it, next to your profile you will see the text "Following"; if you press it, you will see the option to stop following them. In this way, the user will no longer appear on your friends list.
In case the user continues in your friends list, we recommend that you force stop the application and then reopen it. This way, the user should no longer appear on your list.