It really is. Just ask your friend if there's a little switch on the curling iron with two numbers: one number like 110/115/120 and another one line 220/230/240. If so, all you need is a plug adapter. If not, you need a little transformer.

I'm not sure I'd rely on what the Marriott comes back with...rooms can vary and it's just another thing that can go wrong. BEst just to get the appropriate adapters.