It is complete rubbish. It is either Freeman on the Land or one of the related forms of legal woo. There are only four clauses in Magna Carta that still apply today. The rest is long since repealed. The clause on which she is relying (Article 61) was in the original 1215 version but that was quickly declared null and void by the Pope. It was not in the final version of 1225, which is the version that forms the basis for our common law today.
The other problem she has is that, even if Article 61 was still in force, it only gives rights to 25 barons. She is clearly not a baron.