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It seems that you really have two questions here, so I will answer them, one at a time. Setting up an account with Authorhouse should have been taken care of when she published with them. I am assuming she published her book there? If she has, then she can just register. They have an author center where it allows her to register: http://www.authorhouse.com/AuthorCenter/home.asp
The second question: you cannot find her book unless you knew the title or author name. This is standard in the industry. If you want people to find her book easily, they have a way to set up a website for her, and then you can just tell people what site to go to to buy her book. Here is the link for that:
Hope this helps!