Yes, and? is the look Rey seems to be giving 'Carlisle' right now. The point he makes is good, but there's also no telling whether he's the original or not. Just like how he can't tell if she's the original...

Well. Not unless he was really Carlisle himself.

"So, what do you want? Am not going to kill random people because they might be someone's mimic."

Though when some of them seem more inclined to kill her, such was the case with Firo's doppelgänger, it doesn't take a genius or a magical test to figure things out.