It's the owner of the property who needs the buildings insurance and, irrespective of your joint decision with your daughter not to have a formal tenancy agreement, you are still a 'landlord' and the property is not hers.
I think you will find that it is a standard proposal question when applying for buildings insurance that the proposer confirms that he/she owns the property.
That's why the various companies are saying what they are saying.
I don't see why you need to come back to the UK to fix this - you could buy a policy from a UK company whilst in Spain.