It doesn’t matter. That’s what bitachon is – whatever happens, we know that Hashem is looking out for us, and it’s for the best.
How do you know what might have happened if you hadn’t davened? Maybe she would have died sooner? Maybe she would have lived in excruciating pain for a while before passing away?
The fact is, we don’t see the big picture. Hashem does, and He listens to all our prayers.