I don't think we agree at all. I know Ivy is a slut (we have her own words to that effect). I just don't agree that she's the biggest slut in this game. If all the things she's probably getting up to, outside of gameplay, were instead featured in the game, then I would have to agree with you people. But they're not, so it's not actually part of the game. And no matter how many times some people try to say that it is, it won't make it so.
In the case of Jessica, she had a much higher profile in Good Girl Gone Bad, than Ivy does in this game. Because one of the main focuses of that game, was Ashley modelling herself on Jessica and then eventually superceding her. That resulted in Jessica featuring in many more sex scenes, than Ivy does in this one. I mean so far we haven't even seen Ivy with a man, except that one brief BJ scene with Jeremy, at the end of Truth or Dare. So it was easy to say that Jessica was a big slut in Good Girl Gone Bad, because we actually saw lots of evidence of it. Whereas, with Ivy we only have a few lesbian scenes and an awful lot of maybes.
Ashley starts off Good Girl Gone Bad, as a relatively innocent girl, with limited sexual experience. Whereas Lena already has quite a lot of sexual experience, with many different partners, and she's already confident enough with her body and sexuality to pose nude in public. After her relationship with Axel ends badly, she temporarily loses some of her confidence, and it might seem to begin with that she's similar to Ashley at the start of Good Girl Gone Bad. But she isn't. Underneath that illusory shyness, there's a temptress waiting to re-emerge. And although she might appear to be the sweet girl that Ian initially envisages, there's also the girl that was corrupted by Axel and Ivy, and has the potential to be slutty and deceitful, if the player allows it. It doesn't take Ivy's intervention for Lena to succumb to Mike's charms. She's already become his slut long before Ivy gives her drugs, and she knows that Mike has a girlfriend, so she's effectively doing the same thing that Cherry did to her. And she apparently has no real problem with that. On the contrary, it turns her on even more.
So this idea, that Ivy is primarily responsible for Lena becoming a cheating slut is nonsense. She starts the game with that potential, and the lion's share of the corrupting was done by Axel. His deceitful actions, the kind of relationship he manipulated Lena into and the idea that it was ok to cheat, all comes down to him. Ivy has always been clear, that she doesn't believe in getting tied down. She believes that girls like her and Lena should stay single, so all these complications that Lena is currently dealing with, never materialise. She's adamant that Lena shouldn't get into a relationship with Ian, precisely because she believes that Lena will find it difficult not to cheat. And even if she doesn't, she's constantly struggling with temptation, because her natural inclination is to flirt with people she finds attractive. And that's not down to Ivy, it's entirely down to the kind of person that she is. Maybe when they were teenagers, Ivy played a big role in making Lena more comfortable with the idea of being slutty, but for a long time she's either been mainly influenced by Axel (they had a master/slave relationship, and she pretty much did whatever he suggested) or more recently it's been Seymour, who's convinced her that people like him and her can have it all, and ordinary mortals are just their playthings.
Seymour is very likely intending to mould Lena into a total bitch, who's the equal of the controlling bastard that he is. All that discussion about the 'The Child' and how they're destined for greatness, by controlling lesser mortals. He believes that Lena can be just like him, if she's given the right guidance. I guess it's lonely at the top, and he wants a companion, that he views as his equal. But of course, that will likely be at the expense of everyone in her life that she currently thinks of as a friend.