Same old nonsense, I guess she got a non-approved vaccine in Germany, or anything else, including perhaps no vaccine at all.
This is the regularly updated list of approved vaccines from approved countries. Spain is on it. Has been for ages, my preferred source of up to date information over the The Mirror:
https://www.gov.uk/guidance/countries-with-approved-covid-19-vaccination-programmes-and-proof-of-vaccinationRelevant sections:
To qualify under the fully vaccinated rules for travel to England, you must have proof of full vaccination with a full course of an approved vaccine. The proof must have been issued by either:
the UK or UK overseas vaccination programme
the United Nations vaccine programme for staff and volunteers
one of the countries or territories listed below
...
You must have had a complete course of one of the following vaccines at least 14 days before you arrive in England:
Oxford/AstraZeneca
Pfizer BioNTech
Moderna
Janssen
Sinovac-CoronaVac
Sinopharm Beijing
Covaxin
...
Spain EU DCC. You can use this to add proof of vaccination status in the UK passenger locator form. You must be fully vaccinated with an approved vaccine.