But seriously, the entire "I've seen that before" thing is totally interesting?
Yes, yes and yes.
Oda did this recently with Duval and here again we see it played out, why do I get the feeling this time it isn't a joke.
So the eyes seem fake. She also doesn't have any respect for the history of the island and its people so she'd have no issue duping them into believing a tale of grandness. Or maybe it's a half truth. At any rate, Luffy sure as hell isn't stone and we've got something he's seen before. Tattoo? Type of scar? Memory? I'll throw my hat in the ring by saying, I think it might be something even if we see it, we may not understand it at first. We could easily assume if Luffy's mother was associated with this island it's somehow related to his mother, right? And if so, it's a mark she bore as well. That's the simplest route and although I'm not a big fan of that, Oda could make that work. I'd like to think maybe a design he recognizes? Dare I say, somehow a FACE? Maybe not even a human one at that.
How about I really stretch things and suggest maybe there ARE eyes there, just not a Gorgon's. Who else has eyes that are so characteristic they could leave an impression on even Luffy? A certain swordsman perhaps? I'd enjoy seeing Oda explain that one, not to mention why she'd have to hide them.
Dare I be so bold as to suggest she bears Skypiean/Shandian wings? There's a conspicuous puff of steam right around the small of her back that could be said to conceal them if they're bandaged up.
And one more thought, perhaps her leaning back, while a great gag, is more complex than simply a gag.