What position do you understand ?
That a bank can't have an employee who handles their money but can be manipulated over the phone to open their heart, leave work, and open their purse to a stranger (even though a bank customer in this situation). Next time, it might be the bank's money or the employee's well-being at stake.
I don't think she's a bad person, but I can see how the bank can view her as a vulnerability to them and possibly to herself. I can agree that firing is overly punitive if she was an otherwise promising employee. I can also understand her not wanting to work for US Bank for their draconian action if there were no opportunity for retraining or specialized training for such situations.
She sounds like she'll land on her feet after this and I hope she does.