You are an angel for doing this. She is a little cutie pie! When we first got Hot Rod, I read that you can try to put a clock that ticks close by as it sounds like mommas heartbeat. I tried it and don't know if it helped or not, but it certainly didn't hurt.
Also, they have those "perfect pets" that you might try. It is a stuff toy dog that mimics a sleeping dog breathing. Maybe this will give the puppy some comfort to snuggle next to it and curl up with it.? Best of luck.