As a character, she IS non-threatening. For one thing, she's a sex object. A love interest. That is essentially her character. Or at least, that's all I got from her. There is never any question that she might do anything other than marry a) Jake, or b) the other guy. Whatever his name was. She may fight, she may be "spunky", a skilled warrior, whatever - all of this is negated by Cameron making her SEXY. That's pretty standard in modern society - a woman with power must be made non-threatening by turning her in to a sex object/love interest/wife. Which Cameron does, quite successfully.
I posit that her fighting, being spunky, and a skilled warrior is what makes her sexy. For that matter, the entire Na'vi people are sexy, the males included. I don't think there is any misogyny there, except that which the viewer brings.
And I for one am tired of the PC nonsense that tells women they CAN'T be sexy. To be appealing to males on a sexual level is to negate everything else about you.
Nonsense.
To imply that James Cameron is sexist in any way is a bit far-fetched IMHO. Not after Ripley and Vasquez in "Aliens", Sarah Connor (especially in "T2"), and even Max in "Dark Angel".
However, there's a certain pattern in Cameron's movies that during or shortly before the climax (no pun intended) the male hero is killed or otherwise incapacitated so that defeating the villain is up to a female character.
In "The Terminator", Kyle Reese is killed by the Terminator, and the Terminator is then "killed" by Sarah Connor. In "Aliens", Corporal Hicks is badley wounded and Ripley has to go rescue Newt and kill the Alien Queen on her own. Finally, in "Avatar" Jake Sully is incapacitated and Neytiri is the one who kills Colonal Quaritch. "Dark Angel" is perhaps noteworthy because the character of Logan Cale is bound to a wheelchair, which limits his fighting skills and leaves the more physically challeging tasks to Max.
However, Cameron is alternating between male and female protaganists and therefore also between the genders of their respective love-interests.
Aliens: Ripley - protagonist, Hicks - love interest
Titanic: DiCaprio's character - protagonist, Winslet's character - love interest
Dark Angel: Max - protagonist, Logan - love interest
Avatar: Sully - protoganist, Neytiri - love interest