It’s not fanservice if it’s in-character.
A random Asari being sexy in an ad is not fanservice. They routinely exploit the fact that the rest of the universe wants to bang them.
Miranda, who resents her origins and gifts, walking around in a skintight catsuit is.
If such a distinction can’t be made, then it rules out ever having sexy characters in any context ever without it being problematic. Which would… be problematic.
I don’t think Miranda resents her gifts. She’s very straight-forward about her design as a perfect human: attractive, healthy, intelligent, and depending on who you ask, charming. She goes so far as to say this is “just a fact.”
I believe it makes sense she’d take advantage of her assets. She knows she’s beautiful. She knows she can use it, and she does, because in addition to her arsenal of other skills her sex appeal makes her feel useful as a person.
Even if you’ve romanced her or cemented a friendship, she continues to be the same sexy, aloof person you met in the first place, but with an added confidence of knowing that’s not all she is anymore.
But her origins? Yes. Definitely resentful.