I have never had a female friend who was into porn - but my stance might skew things.
However I have known women who:
-Advocate porn for reviving failing relationships
-Advocate porn for making a man change his mind when he says he wants out
-Demonstrate how 'cool' they are by purchasing porn with men
- Use porn with a partner to get in the mood
-Advocate porn as part of a seduction
All of the above women have had the kind of un-enviable relationships where they are uncertain about being wanted or respected.
I also know women who hang out with gay men and watch amateur porn - because 'its a laugh'...
I have never known a woman who uses it to masturbate or talks about that. Perhaps they are more uptight about admitting it than men, but my feeling is that women are more easily turned-off by porn than men and huge numbers of women actively dislike it.