This is the section you’re referring to:
But the week before Warren went into labor, a cashier at Chick-fil-A said her debit card had been declined. She prayed it was a mistake, but deep down, she knew: The cash was gone. She couldn’t even buy a chicken sandwich.
That says cash and debit card, not a maxed out credit card, and it was well after she started working for Uber. Remember, her initial goal had been to pick up the gig to pay off the debts.
And yes, she pawned a ring for the down payment. That only means she didn’t have that kind of cash just sitting around. Again, I never claimed she had a savings from which to draw.
However, that has no bearing on one’s credit level. You can have good credit without having much in the way of spare cash.