The passport is a legal documentation, NOT a proof of her breeding!
You can obtain the passport trough a number off sources for instand the KWPN. If she is a KWPN horse, then she should have a breeding certificate.
I'll inform SANEX of your post, she recently had a question about her horse who was sold to England, but the pictures off the horse showed a different horse, traveling on the documents of her horse.
My quess, since the documents are in Dutch, people in Brtitain are fooled bij false papers. I agree with Oestinja, it looks like a Frisian crossbreed!