Ariana isn't cheating on the Vanilla route. I mean she's flirtatious with some of the male characters ( especially during Chapter 1), but that's just the kind of personality she has, and not indicative of her cheating on Alex. During Chapter 1, a lot of that content related specifically to NTR scenes, and the NTR content was simply removed, and what remained became the Vanilla route. So it might have given the impression you're suggesting, if you don't realise that, but I doubt that was the intention of the Dev?
During Chapter 2, everything changed and the Vanilla route, suddenly had all it's own content, and Ariana became almost obsessively determined to be the perfect girlfriend for Alex. In Chapter 2, if anything, it's Alex who is the only one who could remotely be described as cheating. Because he can't stop hanging out with the girl, he was once madly in love with, and for some bizarre reason can't imagine why his current girlfriend might be just a bit bothered by that?
On the Vanilla route, Alex seems to be at his most infuriatingly naive and gullible. He just never picks up the very clear signals that Queen has come to insinuate herself into his lovelife, regardless of whether he's moved on and now has another love interest. Even when she's telling him that she never stopped loving him, he's still not really getting it, until she kisses him and then everything suddenly clicks, and we have the 'duh' moment.
I've got to be honest. I don't know what either Ariana or Queen see in Alex? Because he is just so dumb a lot of the time. Queen must be a total glutton for punishment, because first time around she gave him like a million hints that she was interested in him, and he never picked up on any of them. And years later was still oblivious that she even had feelings for him. I mean even his loser sidekick Marty worked that out.
