A lithe, athletic girl in a tight-fitting leather costume is not a significant improvement, in feminist terms, on a whore.I'd think this is true for certain values of "whore," but if the author believes that they're both morally neutral (as I would contend), it's not coming across. Sexuality is part of the human experience. Is there anything necessarily disempowering about sexualizing yourself? What if another facet of your persona is the one being accented? That whores and other sexualized women are more considered objects than persons is a function of sexuality's place in our society, not anything intrinsic to sexualization.
A female character who embraces her sexuality (or even sells it!) can be a "strong," "convincing" woman character. She may not be taking the speculation part* of the speculative fiction where you want it to go, but that's a matter of taste, not evidence sufficient to find the book anti-feminist. In fact, it's possible that the speculated setting could be one in which women can embrace many aspects of their personhood, including their sexuality, without the baggage and judgment and disempowering objectification that make doing so problematic in our world.**
It's one thing if you are bored with male writers defaulting to prostitution as a job for their female characters,*** but there's no need to imply that hookers can't be three-dimensional when the problem can much more easily be attributed to bad writing.
* I don't care if your imaginary world has perfect gender equality (or even eliminates one gender altogether), if the characters are Homo sapiens, then they're going to sexualize themselves and others. Maybe that's not the focus of your book or your protagonist is relatively asexual, but my suspension of disbelief will not extend much further.
** I willingly admit that this is not what is happening in a lot of SF/F with sexualized female characters.
*** I'm bored as hell with writers using writers as characters: that's even more lazy and gender neutral to boot!