There is a book,
Bound By a Mighty Vow, which I believe is coming out soon that deals with the early history of women's fraternities.
Amazon.com description
Not a book, but a website:
History of the Women's movement via Kappa Kappa Gamma timeline
(click on "Launch Women's Timeline")
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From my reading, she attempted to go in as herself, undisguised, but was "shut down" so in order to really "infiltrate" these sororities, she had to disguise herself--so much to where the four women she profiled would not recognize her as she is normally. We don't know how she approached these girls, don't know what story she gave them or how she befriended them. She could have said anything to get them to agree, which to me is a questionable practice, bait and switch if you will. But, I'm not familiar with qualitative research, so maybe this is okay.
I think I've mentioned it before, but my biggest problems with her book lie in her sources--some of which are out-of-date and questionable (including websites) and her attempts to generalize Sororities through her four profiles and (hundreds? thousands? the number is unclear) of interviews. I would be slightly more comfortable if she stated that this is what life is like in those two sororities for these for girls at that one campus instead of making it sound like the findings in her book is what happens at all sororities on all campuses all over the country and Canada.