In addition to everything every one else said (which was all completely accurate)... I would be more concerned about attempting to switch her over if she was an older snake.
Since she is an '08 you shouldn't have too many issues. Of course, there are always those stubborn few, but I've found that you have about 8-11 months after hatching where you can easily switch them between mice or rats and live, fresh killed, or frozen thawed.
Most of my hatchlings start out with live rat pups. Depending on when I plan on ordering my next batch of frozen feeders they may get live rats for the first 2-8 meals. I've never had a problem getting them to switch to frozen thawed. I've had a few young "mousers" in the past and the only ones that I had any real difficulty switching over were those that were roughly 11 months in age.
If you like the snake but aren't sure about it eating mice you could ask the breeder to start feeding her rats instead. Most breeders don't have a problem attempting the switch before they ship - especially if you are spending that type of money and you have already paid (or are making payments). The weather is pretty nasty right now (at least it is in Minnesota) and most breeders won't ship for another few months which should be plenty of time for her to be switched over to rats (live, f/t, f/k... whatever you prefer or the breeder has access to).