I understand you're worried - but I've always worried more about properly thawing the food, over my live food source. The pet store I go to has a pretty good reputation and history and I don't worry too much about it.
I don't know if she will prefer it over f/t. You have to try
I thaw them for a few hours, and usually use a human heat pad set on the lowest possible setting.
I also have experimented around with putting them in a plastic bag in hot water.
Both methods work. It's just a matter of comfort for you.