Well, they did and they did. You can't change facts. You can't change history.
Doesn't make what they did any less unpleasant, but they did have that previously hidden side and they did do it. Refusing to accept that fact is utterly pointless because it has happened, just as pointless as wishing that the stars aren't in the skies, an apple is a pear or that a glass somebody drops on a stone floor hasn't smashed into a thousand pieces.
And no amount of ruminating, fixating or obsessing about it is going to change the facts. It's just going to dictate your life and functioning until the point at which you can say 'Enough. It happened.' and direct your attention outwards where you can find something more interesting and more rewarding than that to think about and experience.
As an aside, I note your username:
You don't have to try and be neurotypical. Like that person being one thing you'd been led to believe when fundamentally, they weren't, you're not neurotypical. You're Autistic. It's a fact. You can't change it and it's pointless to try and tear yourself apart to try and be literally somebody else. There is nothing wrong with you as you are - because it is you. It is your fact, which isn't wrong, it's different to some people, but similar to millions of others, yet still utterly unique.
Neurotypical people struggle with betrayal, loss and identity, too. Some find it harder to adjust to major changes or losses than others, in some situations and not others. They are also unique in both their similarities and their differences, every last one. Emotions, feelings of confusion, hurt and pain are felt as keenly because it's a fundamental part of what it is to be human.
You feeling pain at what this person has done is absolutely normal and typical of humanity. Some of the things you have tried help some people, others would find them pointless, uncomfortable, faintly ridiculous or just not right for their particular situation and for them. Some could just as easily try to find other responses that are completely detrimental - obsession, stalking, violence, risktaking behaviour, intoxicating substances - and some can move to accepting something quicker. It doesn't mean it won't hurt, there's no law or human brain make-up that says you have to like what's happened. But it's happened and what matters is whether you mentally stay at that moment or whether you look ahead to a time when it isn't the most important thing in your mind all the time.