Is there a plugin to Prevent Comment Viewing….

I’m in a situation where I created a blog for my daughter and her friends. I’d prefer to have it where the content of their “gossip” can only be seen by members of the blog. I was thinking that a plug-in which prevented comment viewership without membership would do the trick. I searched around but I haven’t located anything.

Is there a plug-in to prevent comment viewing before a visitor logs in? If so can you link me?

thanks in advance