Citizenship is a red herring. Neither the contract nor applicable law, in this case EC 261/2004, distinguish rights by citizenship. Your companion is equally entitled to require a refund under the Regulation, not because the companion is Spanish, but because both flights on this ticket originate in the EU and this is an EU carrier.
The companion ought to make the request for a refund, wait 7 days and then initiate a chargeback with the companion's credit card issuer (bank). Supply the e-ticket receipt, the notice of cancellation, the request for a refund, the denial of a refund (or note that no communication has been received), and the assertion that a reimbursement (refund) is due under EC 261/2004 both because TP is a community carrier and the ticket is a departure from the EU.
Ultimately, if the companion is based in the UK, whether a citizen or not, the companion could also initiate an MCOL action in the UK or, if not, a small claims action (hearings held via telephone). But, that is well down the road.