The best way to help in this situation is:

1) Cellphone video of harassment
2) Get her contact information if possible after TSA and LEO is done harassing so you can share it with her or offer to make a statement on her behalf as a witness
3) Send cellphone video to news outlets and publish online as much as you can to highlight harassment
4) Get the GA's name who initiated things and follow up with the authorities and the employer. Making false reports is a crime, too.

Trying to intervene once law enforcement is dealing with someone is a horrible idea in my opinion unless you have plenty of time and money to be principled and see things through. Sad, but true.

The only thing I could see someone reasonably doing without getting swept up in things is going up to an LEO (a real one, not a TSAer) after the situation seems cooled down and offer to give a statement and your contact information as a witness.

peace,
~Ben~