Is that in the spirit of the law? I could see a fine, scaled to personal wealth. But imprisoning them, what threat did she actually pose? What were the worst possible consequences of massively profitable companies not talking for a bit?

New Zealand, you disappoint me. Looks like the judges got owned by the oil industry

To be facing 10 years she must have been charged under section 255 subsection 1 of the Crimes Act 1961. It doesn't seem from the article that her intentions met the criteria in that subsection which states "Every one is liable to imprisonment for a term not exceeding 10 years who makes a false document with the intention of using it to obtain any property, privilege, service, pecuniary advantage, benefit, or valuable consideration."