>>>She will have a county court judgement against her name if she does not pay
Not if, as the question seems to imply, it's a limited company. A limited company and its directors are entirely separate legal entities.
>>>the judge agreed the papers can be served to the letterbox at the company
Legal notices can always be served by delivery to the registered address of a limited company.
>>>I am thinking to get a police warrant
The police can't get involved in civil matters. It would only become a criminal one if the court issued an arrest warrant for contempt of court (for failing to obey a summons). Civil courts hardly ever do so.
If your post refers to a limited company which has gone into liquidation, you need to contact the liquidator to add your name to the list of creditors.
If your post refers to an active limited company (or to a sole trader) with a bank account in this country, you could try getting a court order to take the funds directly from that account (but, unless you've ever received a cheque from the company, tracing bank accounts can be nearly impossible).
If all of the company's assets are in Spain, you might need to seek action through the Spanish courts.