I disagree with her and agree with you. You wrote it, they liked it, done!
Also when someone normally wins something, many lost. Does God somehow like the winners better? How does that work for the losers. Do they now know God likes them less? How about when mom dies of cancer and someone else makes a recovery. Does god dislike your family?

I'm with the majority of people here who say just agree with "Yes, dear," or "whatever" and move on. You know the truth and it seems she was trying to egg you on into a discussion you obviously didn't want.

Thank her for the effort and support the same way you would acknowledge anyone telling you they sent good thoughts your way.

I can see this happening to me in the near future at family events...

It's hard with someone you love and care about, in this situation she's purposefully being mean, so I would just reiterate that I wrote it not, God. But I'm also a passive person (sometimes...passive aggressive) so I'd probably go "whatever" and drop it. Usually I'm a lot nicer about stuff and would let it go but something like that would definitely irritate me.

does that mean the other people who prayed just didn't pray hard enough

This is one of those moments when "Yes, Dear", and a smile, come in handy.

You're not likely to change her thoughts on things, any more than she will change yours.

It could just as easily have been the Flying Spaghetti Monster. If you're not familiar, the FSM is the make believe entity that takes the place of god in those conversations.

I always as anyone who is trying to have me credit god for anything th prove the existence with actual scientific evidence. That usually shuts them up!

Cognitive dissonance.

[simplypsychology.org]

You don't even try. You just say "Yes dear" and leave it at that. In that situation you had 2 strikes against you, 1 she was a firm believer, and 2 she was your wife, end of story.