I'm going to assume 10 minutes not hours, haha.
You could probably avoid bringing your snake if you do 1 of 2 things.
1 - learn the weight of prey your snake needs and bring a scale. If you don't know, you can weigh your snake. If it is young/still growing take 10% of that and ask for feeders around that weight. You can bring a scale and get ones in the ballpark of that weight and buy for whatever she calls them as. If your snake is an adult, you can just ask for rats in the weight range of the way they're usually sold online (smalls 45-90g, medium 90-170g) or at the store you used before.
2 - measure and go by girth. Put your snake over paper and draw lines on either side of her midsection. Take this with and aim for rats about the same width as that. (This is the way folks who prefer going by girth to feed would do it.)
As someone who breeds feeders now and has animals from larger lines, I find that the ages don't match the weights from those charts in my animals. By 3 weeks old, my rats are pushing into small rat size 40-60g. By 5 weeks they're mostly medium rat weight ~90-100g.
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