I'm a male and write a lot of female protagonist storylines. So, rather than "female character", you're asking about "female object of desire"?
That's how I read it too, and in that sense, nothing is sexier to me than a someone who can hold a conversation, and the more argumentative, the better. (It's terrible. I'm a feminist for all the wrong reasons *sigh*) This translates to female characters who are capable, intelligent, and either subvert or totally discard typical tropes that plague them. In Duskford's "At the Cabin," I have a particular fondness for Heather Ravers in this vein, particularly after Cretan Bull's comment comparing her to Alexandra Daddario's female lead in
San Andreas -- a young woman with street smarts, social adroitness, and determination beyond her years and station. (In the story, this is one of the reasons why I enjoyed the Zack/Heather pairing -- Zack, by and large, can keep up with her in all respects, and Heather, for the first time, feels the shoe on the other foot in trying to chase him as opposed to the other way around, humanizing my characterization of her in a sense.)
In the end though, I just prefer women in stories to be on par with the men, and I try very hard to do that justice. Sex is always steamier between two people on the same level.
Most of my female leads are based either on my wife, or things I've done with her or seen her do, so I'm a little biased I think. But often enough in my stories, my female characters are usually strong willed for the most part. I mostly like the ones that are matured emotionally and intellectually due to their experiences. I like to have my characters grow from sweet and innocent into something more.
Development over time is fascinating, in that one sees why they have the proclivities and tendencies they do. (Re: Dahlia from your story, Fallen

)For sexual fetishes and preferences, this is largely through conditio
ning in childhood and adolescence, and that can be powerful in a story if that relates to the ongoing plot. Emotional and intellectual development separate from sex is always entertaining to me anyway. Character-based stories aren't as stressed to conform to a certain moral or allegory as plot-based stories are, and seeing people as act people doing things, no matter how irrational or insane, that people do has a lasting impact. John Carpenter's remake of The Thing will always be the scariest horror movie alive for me, because everyone acts the way I expect people to act if they were being infiltrated by a shape-shifting eldritch horror from beyond the stars. Nobody holds the idiot ball and does something that prevents everyone from being saved à la Gilligan. They're fucked, and the moment they realize that at the end... well, my wife had repeatedly said that it would be her, a pistol, and a spray bottle of Clorox at the end of the world, just like Kurt Russel.
On a side note, one of the first major papers that looked at the development of sexual preferences and fetishes over time -- Relative prevalence of different fetishes from Nature -- looked at a large dataset from Yahoo groups and largely confirmed the conditioning hypothesis, though it did examine claims that such fetishes are inherited. That lead to this fun quote: "It is unlikely that a particular genetic makeup should result in a preference for specific stimuli such as, for instance, coats, balloons, eyeglasses or headphones – all of which we found in our data." Also, good news for foot-lovers, as that seem to be the most common fetish according to the study.