According to Spanish media reports on Thursday and Friday, she is suspected of being involved in the sale of works of art belonging to the Poor Clares community, of which she herself is no longer a member.
The former abbess spent the night in custody, according to reports.
Meanwhile, one of the nuns, visibly upset, explained in a video she recorded herself: "They arrested the mother and we don't know why ... We don't know any reason that could have made them do it!"
The police operation began early on Thursday morning under unusual circumstances.
As the doors of the monastery remained locked and all attempts to contact them by telephone failed, the officers had to unscrew the mechanism of the entrance gate in order to enter the premises.
It was only about half an hour later that the former nuns opened the convent door, whereupon the search began.
In the afternoon, the investigators left the premises together with the arrested ex-abbess.
Several criminal proceedings
The community is currently involved in several criminal proceedings.
One case concerns the sale of 1.7 kilograms of gold worth 121,000 euros.
In a further case, the Papal Commissioner Mario Iceta filed charges of serious fraud.
They are also investigating whether they attempted to transfer the monastery's assets to a civil organisation.
At the same time, eviction proceedings against the excommunicated nuns have been ongoing for over a year.
The conflict surrounding the Poor Clares of Belorado has continued to escalate in recent months.
In May 2024, the nuns published a manifesto in which they renounced the Catholic Church.
They also declared that they would not recognise any popes after Pius XII (1939-1958).
Furthermore, they joined various alleged (schismatic) bishops.
Finally, they were excommunicated on the grounds of schism.
All attempts at conciliation by the papal commissioner Iceta failed.