Like everyone else said, I would just try to not get white rats if she won't eat them.

But on the note of the rat getting out, I personally wouldn't feed my snake a rat that had been missing for a few days. There is no telling what the little guy got into. I'm guessing since you still have him he didn't get into any posion, but that is only a guess. There are many things that rats can get into, and I just don't think I would want to take the risk of feeding a rat that could have been exposed to so many different things that I don't know about.