Did you consent to an open relationship or imply an open relationship? Assuming you said no... she made plans to leave and cheat. It's not like she was drunk and opps, something happened that she regrets.
So... she's aspie? And you're NT. Ugh... well. Hmmm. It's likely she knows exactly what she did. To protect her lie from you and herself, she's essentially going:
Lalalalalalalala i can't hear you! Or myself. Lalalalala.
How can she lie like that, she has to, it's so obvious what's happened.
What's really concerning, is she may want you to hate her to bring balance to the aspie-force. So she might start using you, or already has, in order to bring the relationship to it's inevitable conclusion. The same result she has with all her relationships.
There's a difference between growing with your partner and one partner trying to do damage control on the other.
She has feelings enough that she knows what she did. She is logical enough to have sealed those feelings off.
It's done. You can't do this kind of repair work unless you're in a trusting relationship. And yes, she likely cheated on you again. That's why she's blocking it out. Nobody likes being proven a fool.
P.S. This doesn't have alot to do with aspies i don't think. There are SOME elements (like sex drive maybe, or being able to block empathy... and this is clearly on purpose).
To be fair, i wouldn't break up with her myself. But that's a story for a different day.
You can always cut in viciously (figurative) and see what you find. Not recommended.
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Formerly I 80% N 85% T 80% P 15%, INTP, philosopher. Now E 60% N 65% F 90% P 15%, ENFP, ray of sunshine, unless i'm moody.
It clicked one day. I have empathy now. It has downsides i didn't expect. It's going somewhat poorly, since people tend to suck at new things. That's how you know it's true.