Eh, changing your name in the military can take years, mind you, the process to officially change your name is fairly quick, it's just that then someone has to go in and change your name in every website and system your name appears in (and by someone, I mean multiple someones, because no one person actually has access to all of those, and likely they'll still forget a few)
So it is entirely possible that she could have chosen to just not change her name within the military to not have to bother with it