This article by Tasha Robinson should be required reading to all writers (especially male writers, like myself) who like to think they are writing strong female characters. Perhaps you are, but Ms. Robinson gives a good checklist to contemplate.
A big thing she talks about is the "Trinity Syndrome"-- where a female character is given the impression of being strong and important-- like Trinity in The Matrix-- but after her strong and important introduction, she actually contributes very little to the actual plot, other than propping up the hero. Or, as Ms. Robinson so eloquently puts it, "A sexy lamp with information for the hero written on it."
This is not something I get right all the time, myself. Thorn of Dentonhill, I'll admit, has only one significant female character in it, but she is pretty crucial to the plot, and it involves being Veranix's friend and confidante, but not a romantic partner. I may not have done a perfect job, but I strove to make sure that Kaiana was not a sexy lamp. Is she a Trinity? I don't think so. I can tell you, if she veers in that direction in Thorn, I'm fairly sure I turned out of the skid in Thorn II.
A Murder of Mages has many significant female characters, including and especially Satrine, who is very much the co-protagonist. No one there is a sexy lamp, and Satrine is definitely not a Trinity.
That said, this gave me good things to think about, and places where I can see room for improvement in my own work. Which is always the goal, right?