She wants to allow others to blog in her blog :-) not just comment about what she blogs. Look at your "users" and you can add other people and even give them admin priviledges in your blog if you want. However, they have to already be signed up to have their own blog, be part of the PC blogging community. Since you have to register for a blog, that's the only registration the blog software knows; that blog registration, not the PC registration.

But you can make your blog your own private "forum" that way, turning off comments and/or viewing or whatever combination if you only want your group to see and talk together.