Wasn't she already wanted for some unspecified crime though? It's something they glossed over in season 2, but in her initial appearance she was clearly on the lamb and had reason to believe that the Republic would send hunters after her and if caught, would see her rot in prison for life. That has to be a little more than just desertion, and IIRC the implication was it was for things she got up to AFTER leaving the military. Knowing her backstory, I'm guessing it was some post WWII Mossad style revenge assassinations on former Imperials, regardless of whether they defected before Cinder, or were formerly pardoned.