"Still, can you advise where can I find a provision or section of the code that slam-dunks this?"

Yes. Search for the W2 instructions, to learn that Box 14 is for the employer to use for informational purposes.

And: "Depending on the airline, the TAFB ratio is usually somewhere between 3.5 to 4, meaning that for each 3.5 to 4 hours away from base, you’re guaranteed at least an hour of pay."

Per Diem Pay isn't taxable.

And I assumed you meant Washington for WA. I gave that link. Maybe that was a bad assumption?

And your daughter has employer resources that will explain the paystub to her. Does she now understand her pay + benefit structure? Maybe this is the time for her to learn about it, to help you help her.

You didn't need a new Log In at TurboTax; your info here works "there" in TurboTax. It's for everything Intuit.