To be fair, if you look at her quarters, she does tinker with things a lot. So it's not exactly out of left field that she might have the mechanical knowledge to tinker up some jury rigged devices.

I thought there was a bit of a missed opportunity to delve into her training and experiences during the Klingon War. They've used that as part of her backstory, but have given the meatiest stuff to M'Benga and Chapel.