Annotated chess game

OK, if White is happy to play a Sicilian (2...c5).

Black's third will lead to real problems, as White demonstrates. That 3...Nc6 is so risky is really due to Black's hesitant 2nd move.

And Amy should be aware thta b6 can be aswered by BxN, g6xB, that leaves her with a scrambled pawn's line. It has some compensation, though, but here the main problem is basic opening strategy.

Strictly speaking, if there are a lot of pawns on the board, exchanging some will be OK. It's when there are few available that the hoarding should begin... In this position, though, White's clear lead in development as well as the plus piece would justify a more violent policy.

Clearly, the best move for black should have been d6, mostly to prevent d6 from white. Note that white can play this move (after exchanging dsb's) even losing a pawn, since it opens the line for the lsb and provides a good place for the Nc3 too. More than that, black has to be very careful in launching another knight so deep in enemy's grounds, specially after the previous experience  )

Of course, Black ought, if she could, to have avoided some of these exchanges. Unfortunately, it's not so easy to decline exchanging Queens when the choice is to resume a passive position on the back rank (...Qd8 or ...Qf8) and letting the White Q in at e8.

I think I would have tried 16.Re7, here. The White King is in no danger whatever.

What about Re7? A rook on the 7th rank can be deadly!

I agree with x-machine. However, there is something to be said for quiet moves like this when given a powerful position. It can place enormous pressure on the opponent to come up with something. Black has no play, here, the usual situation when a piece down in the late middle-game.

Well, this move gives black a tempo to play d6, that blocks a lot of white action for the moment. Of course that having developed the lsb to g7 (it was somewhat forced in order to prevent mate, since Kf8 is doubious). Moreover, d6 sticks white pieces to the defence of d5 (but white can allow himself to lose it).

...with a discovered attack - nice! I've been on the receiving end of this more times than I care for

Nice piece of tactics! An alternative would have been 22.Bxg6!? hxg6 23.Nb5 d5 24.Nd6 Bc6 25.Re7 with a bind. White threatens Ng5-f7-e5.

well, at least Amy is aware of the threat - complete beginners would probably miss it

Amy is aware of it, it can be seen in the following moves (she doesn't retreat the knight). Anyway, after g6 there is no mate anymore (not inmediately). Anyway, more effective would have been Nxh7+ first. The king has to go to e7, then f4 wins the pinned piece.