Finally, I am paired with Anthea once again. I am Black, and she plays 1.e4 for the first time that I’ve seen, and then it moves on to a Ruy Lopez. I spend 5 minutes here thinking either main-line Tchigorin Def., or Open Defense. I figure that her Expert teacher taught her the main-line Ruy, so the Open Defense might catch her off-guard, particularly by her playing 7.Re1 instead of the main-theory 7.d4.
I wasn’t surprised by her decision to trade the h2 pawn for my d5 pawn, but that wasn’t what happened. What happened next took me by surprise, but not so much, knowing Anthea.
My 16..Kg8 was a mistake, as I should have played ..Qf6 immediately. I was playing hope-chess, hoping she wouldn’t see c4, but then I saw that it worked it out that I could defend, before I played ..Qf6 on my next move. She was down < -2 after my poor 16..Kg8 move.
I hadn't even seen 18..Bc5, threatening mate. Instead, I was planning on meeting 19.dxc4 with ..Nb6, protecting the Ra8.
The real magic was that I didn't even realize until I was going over this game port-mortem that I was up a rook! She resigned, unexpectedly for me, once she saw the queens coming off. Opening theory proved decisive in this one, as Black, although only psychologically of course. She wasn't into merely getting a center-pawn for a flank-pawn she said after the game. So she had seen her blunder, and I had wondered why she seemed smiling/laughing at herself at one point; so this explains it.