11. Qf3+ Kg6 12. Bf7#

Forgetting that Black's queen covers thuis square, and forgetting that moving the White queen off the d1-h5 diagonal leeft the g4-knight 'en prise'. A pity, as 11.Qf3ch would have been immediately decisive. The problem of course when one has such an overwhelming game, is that so many promising lines present themselves that it is hard to work out what works best. Mind you, in this game, when in doubt, White could simply have whipped off black's queen, and then work out how to reel in the Black King.

I was going to say exactly the same thing that Mike said. And, I agree with ION, as to, how you overlooked it. At the time, these were things that I also forgot, but they're very important.

Terrible move: 11....Qxd3 would have made a game of it. Now White has a mate in one move. See if you can figure out what it is.

Here 12. Qh3# was mate on the move.

It's close, Erika. But, close doesn't count because Mike got it. It's easy to overlook, and I would've played 12.Qxd8 which is stronger then the move played since it wins the Queen. But, bringing the Queen to h3 was best since it mates.

Better was Qg3+! Kh5, Be2+!! and checkmate follows soon.

Actually, the move White has chosen is the best...

I agree with ION.

That is true, but White has the wherewithal to put the king away quickly.

It's true, sometimes but not always. As sometimes, you need pieces to work together. That's why we don't just give away material without a good reason. In fact, ION's comment is an example of why.

Now I am surprised to see that this game went on for another several pages. It ought to have ended right here. This bishop check is correct and should win in one more move.

It shouldn't have gone on for several pages. In contrast, though, I am not surprised because just like when I was a beginner, white is missing opportunities here which would've resulted in an immediate win.

a checkmate was in fornt me and did not pick it up

In this case Black had no choice; the king has no available squares. White's unmoved bishop on c1 is doing sterling work.

It's good that you spotted this, Erika. Having said that, 15.Qxg4# would've done the trick.

Yep: this was Black's only move available. White's previous two moves were decisive; now for the 'coup de grace'...

Qxg4#

I see it now I need to get better ate picking up checkmates.

Any of the captures on g4 led to mate, but of course Qxg4# was the best.

White's attack has been ruined. She should probably play 16.Bxg4, threatening 19.Bh5#.

Agreed.

I would've played 17.hxg4 to win the Bishop, but I like the move played even more.

No: this is a very poor defence. Much better was 17...Kg6. Now White has mate in one. Again.

ION is correct.

Qxe6#

now i see the checkmate

Good. You're learning! But now, Black is slipping out of your grasp.

It's good that you see it, Erika. All of those Homework questions are helping these patterns become second nature which is what you want.  

Black seems to insist upon playing to lose the game. 18...g6 would have thrown tougher obstacles in White's way.

Neither is Black! But 19. Bg5+ was immediately decisive.

Apart from tactical considerations, 19.Bg5ch would have gained time, developing with a check. The tactical consideration is that Bg5ch would have been a skewer: forcing the King to move and expose to capture the queen behind it. (A skewer is a kind of reverse of a pin: a pinned piece dare not move; a skewered piece MUST move).

Just as good would've been 19.Qg5+ which does the same thing. But, I would've used the Bishop here. And, what ION mentioned is what I was explaining on your 7th move in regards to a skewer. This move, however, blocks the Bc1.

You have a very good move, still. What is it?

Best was 20.Re1! Bare in mind that your Bc4 is attacking his Be6. But, 20.Re1 would've also pinned the Bishop. Consequently, you would have won a piece here. Sure, this move seems good and looks like you'll get a Queen, but he can prevent that with 20...Ke8. Just as strong, as ION notes below is 20...Nf6 which is how I'd respond as black.

Leaving the Queen once again 'en prise'. There was no real skewer here, as Black could and ought to have played ...Nf6.