I think all you need to do is create a Google account and you will be able to request an invite to her blog.
I think since the new Blogspot privacy rules are stupid, you have to know the email address of the person running the blog. I think if you take the first part of the blog and then add @gmail.com and email her, you might luck out.
It's worth a try. I looked up the new Blogger rules and they changed how private blogs are handled.