In 2012, Alex Dally MacFarlane wrote at length and with eloquence on Feminist SFF: Female Friendships, or rather the near-total absence of female friendships in SFF.
You might recall I wrote, well, er, ranted, about this topic back in 2006. It's nice to see I'm not the only one who notices it's still a THING.
As an aside, I'm happy to report that Tobias S. Buckell, whose Crystal Rain I called out on this issue in my first post, put more female characters and more female relationships and mentorships in The Apocalypse Ocean, which is a later work in the same universe (The Xenowealth Series, Book 4). I highly recommend it.