The Queen herself has reacted (via the media) on commotion about possible tax evasion. It is not about public money but about inheritance via her father's lineage. Apparently the Queen had French ancestors in the paternal lineage who died childless in the interbellum and around WWII. These have left the Queen and her De Mora y Aragón siblings various possessions. The Foundation is about these possessions, so the jewels are no part of these.