I think that, given as you note yourself, Ivy doesn't actually have problem with trying to push boundaries with Lena, or do things behind Lena's back, the idea that she treats Lena and Holly differently is, well, just another presumption the game itself doesn't really support. Wouldn't it be more logical to take things at face value, and conclude that there's things Ivy thinks are okay to do (like fucking a guy she knows Lena is interested in, or making a move on a girl she's interested in) and there's things Ivy thinks aren't okay, like drugging people against their consent?
Seriously, it kind of boggles the mind why exactly people believe Ivy is the sort of a person who'd
drug and rape someone while what,
pretending to be their friend? It's funny that for all the talk about "double standards that give women a pass" she seems to be the only person who get smeared with this kind of talk.
Meantime, fucking
Arthur: Hello, Lena

*audience: wild cheers*
double standards, indeed.