Her current incarnation seems pretty much asexual, which...honestly isn't surprising. Given her past experiences I would imagine the prospect of intimacy on any level is a daunting one for her, as it leaves her potentially vulnerable, and as the Demon-Queen of Limbo, the last thing she can afford is to be vulnerable. You could argue that even her deliberate tormenting of her brother served not only to teach him a valuable lesson but also served the dual purpose of pushing him out of her life (severing one more tie that could potentially be used against her).
My own personal belief is that if someone were able to break through the barriers, it wouldn't matter if they were male or female. The problem is that there probably isn't anyone alive that could pull that feat off. Maybe Kitty once upon a time, but that ship appears to have sailed.
Personally, I'm just glad that Illyana has been portrayed as anti-heroic without being overly sexualized. It makes for a far more interesting character than just the typical "bad girl" character.
All that having been said, I don't know that I could actually call it out of character if Illyana DID end up sharing somebody's bed, though I suspect it would almost certainly be a purely physical relationship.