I'm very fond of the Girlebooks site myself. To get the "relationship" stuff out of the way upfront: I have none officially, though I correspond with the site proprietor, have written a review for them, participated in the forum, and recommended some books to be offered. I recommend Girlebooks on my blog for Jane Austen fans, because I like the books; because I liked and recommended them, I got to know the proprietor in an online way when I asked her to do a guest post on my blog. I am considering submitting some of my own work for publication on the site, both for free and paid.
As far as taking the text from Gutenberg, many, many people do that (I have done it for etexts on my own site). You're supposed to remove the Gutenberg text if you change the presentation, or at least that's how I read it. Laura cleans up the files and adds an attractive cover, which gives them added value IMO. Girlebooks is my first stop when I'm looking for a particular public domain text by a female author.
Also, Laura has presented and recommended ebooks (meaning free public domain ebooks) I would not have heard about otherwise, which gives the site value to me. The free books alone there could keep me happily reading for years.
I don't see a problem with having a focus on female authors. Sandy Lerner (one of the founders of Cisco Systems) purchased a 99-year leasehold on a great house in the UK once owned by Jane Austen's brother and has turned it into a
library dedicated to the preservation and study of the work of obscure 18th-century female authors. It's a focus on an often ignored and under-represented population.