It’s not that easy to change your identity these days and to acquire credentials like hers in a new name. I’m not saying it’s impossible, just not likely. If she had done that successfully at the time, I think there is a chance she would’ve resurfaced for some reason in the time since. Whether by choice or by getting caught.
I completely agree with this. Post-9/11, it became especially difficult for people to change their identity. Many employers (and I would think especially doctor's offices/hospitals) do rigorous background checks & I doubt anyone would get away with this for any length of time. And, even if you did get away with this initially - these types of jobs typically re-do the background checks every several years just to make sure nothing has changed.
In fact, I have actually heard of cases where people lied about something on their initial resume - and, even though they still got hired - these lies were eventually found out after the background check was re-done at a later time.