Hi Mendelsohn,
Welcome to the forum. I don't understand, I would have thought that even the CFO would accept a British marriage certificate without it having to be authenticated by NSO. I mean how will the NSO authenticate it if the marriage took place in the UK.
I would tell her to call them up and find out if they will accept it....... mind you, the ladies at the CFO are not exactly known for being helpful or accomodating.
Iain.