this may sound silly but your daughter may not have blocked her so she can see what your friend has been saying, some people do this, i have facebook but only family on mine, i use it as i have been ill over the last three years and it is a quick way to get in touch with them as they are usually on there phones. i never say anything bad about anyone on facebook, if i needed to confront anybody who said anything about me then i do it with a phonecall. don't bother if your daughter lied, does she know how to block someone or has she clicked the button that says hide messages from this person. stop thinking about and leave it alone.