Here are some of the great women SF/fantasy authors whose names begin with "G":
There is nothing gentle about war or women warriors in Mary Gentle's The Book of Ash series. She writes alternate history and high fantasy. You can learn more about Gentle on Wikipedia and find her books on Amazon.
Justine Graykin is a sister member of Broad Universe. She's written short stories in various anthologies such as UnCONventional (one of the co-editors is also a member of Broad Universe) along with novels. Learn more about her on her website.
Nicola Griffith is the wife of Kelly Eskridge, who was featured earlier in this series. Griffith is the author of Ammonite, which I think I read a long time ago but don't have in my current book collection. Find her online on her blog, Wikipedia, and Amazon.
Finally, let me close with Sally Wiener Grotta, sister member of Broad Universe and author of The Winter Boy, a post-apocalyptic story set in a world where older women use sex to train male leaders. Learn more about Grotta on her website (since her husband is also a writer, the site features both of them).
Do you have any other authors to add to this list? Feel free to add them in the comments.