Everything that ties her name to the proprietary system: authored documentation, training materials, version histories, internal correspondence and a manager's letter on replacement time. Add payroll proving the continuous year and the acquisition papers for the mill.
Build the trail in Canada, where the evidence lives
Specialized-knowledge cases are decided on documents, and the useful documents are internal. Export the formulation model's documentation with authorship metadata, the change log showing which versions Priya released and why, and the training deck she uses with new hires. Save the internal messages in which staff ask her for rulings on substitutions or tolerances.
Ask the plant manager for a signed letter explaining how the system differs from off-the-shelf software, how long a replacement would need to learn it, and what the U.S. mill would lose without the installation. Prove the year abroad with T4 slips and pay stubs covering a continuous twelve months within the three years before filing.
Add the purchase agreement and stock ledger showing the U.S. mill's ownership. If the company holds any patents, registered trade secrets or licences related to the model, include them.
Redact commercial pricing if necessary, but do not withhold the substance, because a petition that describes the system in generalities will draw a request for evidence.