An engineering genius, a demolitions expert, an acclaimed artist, and sufficiently skilled in the Mandalorian combat arts to routinely defeat people who just do that full time, all by her mid to late teens, having also spent meaningful time in the imperial academy.
One of the weaker points of Rebels is that, having made the teenage boy a Jedi (the coolest thing you can be in Star Wars), they decided to balance it out by making the teenage girl every other cool thing in the Star Wars universe they could think of. If she was older, or if they established right off the bat that she was a prodigy, I wouldn't be bothered (still wildly improbable, but not as ridiculous), but they sort of stumbled into making her an all-out engineering genius whose weapon design could not be reverse engineered by anyone else, when originally she seemed to just be highly competent, and on top of all of her other competencies it all became a bit Mary Sue-esque on a character who is supposed to still be 20 in the final season.