As I read it, she has a community license issued on the strength of a non-EU country license, and this means she does not have documented training in how the rules work, what all the various signs mean, and so on.
In my case, I obtained a German permit the hard way. And I mean the really *HARD* way, because in those days you had to know the theory about how brakes worked and other technical details. And practical lessons driving in small villages, cities, and on the Autobahn.
All of it in German language too. Including the theory test. But at the end of it all, I got a diploma and a beautiful German DL (which I miss terribly).
What made my case different was that I had been through the whole EU driving education rigmarole in a way that was no different from any German; and when the UK tried to apply nationality regardless of my diploma, I got upset and appealed.
So I would expect that when they see Shelly's DL, they will say, "OK, that's fine. We know all about this. So where's your EU driving school diploma?"
And then she will say, "Um, I don't have one, I exchanged my US DL for it."
And then they will say, "Well that's just hard cheese, isn't it?"
And to be frank, it makes sense because otherwise people could be driving around and not know what the signs mean and what the rules are. And to be fair, you get a year's grace period in the first instance...