Short story - I made a Simulacrum of my elven PC in a far-reaching plan that, well, overreached. An NPC cast Charm Monster on "El Cim" and, even though we knew it would work, that brought up the question.
I assume it's the same as the base creature but I'm not sure.
I think that's as close to an official ruling on the subject as you're going to find.I found this here:
The simulacrum spell creates a duplicate of some other creature and the duplicate has the same creature type as the original.That seems like a DM interpretation but a fair one. I'll tell the DM about it so she can make her final call.