Sexuality and sensuality are not one in the same, for starters. Ivy could make out with a thousand men and women, but the fact remains that she’s stated countless times that she hates all of humanity, Harley aside.
Let me go into this by saying that being ace/gray does not necessarily mean they won’t ever have sex. Asexuality and greysexuality are complicated, because the titles literally means something different to every ace/gray.
Depending on who’s writing Ivy (and my mood for my headcanon), I switch back and forth between ace and gray. Aside from being quite seductive, we seldom see her do much but BE a temptress. What, with the nature of her powers, it would be hard to do anything else. Also it’s been her character shtick since her conception, and it’s held strong since.
I see her as a very…opinionated Ace/Gray. If she DOES decide to partake in something as carnal as sex, it would entirely be on her terms. It’s not a case of good representation for these two sexualities, considering that can be an accusatory stereotype when we out ourselves to others. They tend to call us “selfish,” but Ivy is a LITERAL kind of selfish.
And there’s also her back story as well. She was a doctor, a biologist, and a man she trusted, possibly loved, and potentially was physical with, made her into a creature. A creature she’s come to love to be, much like Marvel’s Mystique, but it was at first against her will.
Jason Woodrue is only one of the people Ivy has loved that has turned on her in the end. As much as I love shipping her with Harley, Harley has hurt Ivy, too. Basically anyone Ivy has ever loved and trusted has betrayed her at least once.
Also she’s toxic to the touch, except for to Harley. If her asexuality isn’t just part of her, then she might be by choice.
And, again, she views humanity as beneath her :/ It just makes sense.
I also see her as Demi/greyromantic, but this is long enough, I think, haha :)