I'm really sorry you got a 3 1/2 week old hatchling in the first place. Since they don't shed until 7 to 10 days after hatching and then sometimes won't eat for another few days after hatching, how many meals could that baby have ever had before it was shipped out....maybe 1 or 2 at best.

Personally I'd suggest whether it's convenient for you or not, expensive or not, you try this baby on live mice hoppers, then live small adults/weanling mice after she's taken a few hoppers. You need to get a solid feeding pattern set down and get some weight on that baby while you can and if that means live, it means live.