The worst part is I tried for 15 minutes to do chest compressions to revive her. Even though everyone including the vets say she wasn't coming back, you still have to deal with the idea that maybe another few minutes might have made the difference.
Please try not to think that a few minutes might have helped.
Whatever caused her death, if it's so sudden and inexplicable, a few minutes probably wouldn't change anything.
But thanks to you, she didn't have to die muzzled in a cage. It sounds like you allowed her to have a peaceful death instead.
The following may sound dull, but I wish someone had told me this: Focus on the time you've had.
Even if it was only a few days, during those days you gave her a better life.
Belive me, that's is all that matters in the end.