You are mistaken. Original classifying authority means that she can classify things herself up to Top Secret. That is how the term is defined.

She can't unilaterally declassify anything so if another agency sent something classified to her, she could not lower the classification.

If something came from one of the intelligence agencies that was Secret or Top Secret, it would not be sent over the open internet to her public email. That would be a security violation on the part of the sender.

We're in agreement, because I said that the documents sent to her were classified by other agencies and that she had no authority on those documents.

Classified items were sent to her to her private email address. Her server, which she had setup for herself, contained those classified items. That is against the law. It is also against the law to handle classified items in a way that puts them at risk.

She is responsible for the content of her server, and therefore broke the law. That she somehow didn't recognize classified material isn't a defense. The people who sent her the classified materials also broke the law (especially since they may have removed any classified markings from the documents).

By your reading, if someone removes classified markings from classified documents or makes a derivative document with classified information and sends it to your email, you are breaking the law by receiving that document.

If something is not marked properly, the receiver doesn't automatically get a security violation.