I think you're on the right track. It's only one offering, so don't stress yourself out yet.

What size prey was she eating previously? and mice or rats?
Make sure you are offering the same prey (assuming she was being fed the right size prey prior to you taking her home) and make sure your prey is the right size. What is her weight? I'm assuming she's still pretty small, so a small mouse or rat fuzzy would probably be your ideal size prey.

You may need to experiment with defrosting techniques and feeding techniques, as some things work miracles for some snakes/keepers and don't work at all for others. For example, my BP won't eat prey that I leave out to defrost. He will only eat prey I defrost in hot water and feed him as soon as it's defrosted and warm. If they prey sits out at all, he will refuse it. Odd, I know, but that's BPs for ya!

I probably wouldn't worry about braining yet either, I would leave the prey intact on your next attempt. Maybe resort to tricks like that later if need be.