> I haven't played running it twice but it looked like there was still importance to secrecy before the second river was flipped given the way they were acting.

No, there isn't.

In tournaments, players are forced to put hands face-up when no more betting can take place. This is in part so people can see there's no cheating/collusion going on, and in part because it's better for TV.

In cash games, there's no such requirement. Players often don't show their hand because they don't want to give away information to the other players. There's rules about who has to show first, but if she had lost the pot, she could have folded without showing.

> Assuming the cheater doesn't know the deck (which would be extremely hard to pull off)

The insinuation is exactly that, that she knew the deck. (Rather, that software knew the deck and alerted her to a favorable position)

If you're not up-to-date on how that can happen, I suggest you review the mike postle scandal, and other proofs of concept where people are, in fact, reading the state of the entire deck.