I guess versus mode is kinda like fighting the AI in fighting games in that regard; They can execute moves instantly and read your inputs / instantly take advantage of your mistakes, so you pretty much have to cheese the AI to win.
I think there are a couple of key differences in play:
1. Arche has no charge moves, and very few roll moves. Most of her attacks are of the "tap direction + attack" variety, so the AI doesn't have any particular execution advantage over a human player.
2. The notion of "reading your inputs" requires some unpacking. The AI isn't a little man inside your computer watching the action on a screen - the game-state, including the state of the controller, is all it has to go on. The question isn't whether the AI "reads your inputs", but whether it reacts to those inputs more quickly than a human opponent plausibly could. Mostly, this means: does the AI start to react before your attack animation begins? As far as I can see, this isn't the case. Even at the hardest difficulty levels, the AI isn't pre-empting your attacks; mostly, it just parries or dodges in response to
being approached. You can fairly easily fake it into dodging a nonexistent attack by approaching it as though you're going to attack, but not actually hitting the attack button - which is the sort of thing you'd expect to work against a human opponent, too.