I think you might be looking at this the wrong way. Credit card authorization occurs in miliseconds but is still a good anti-fraud measure. If her ESTA applica

I think you might be looking at this the wrong way. Credit card authorization occurs in miliseconds but is still a good anti-fraud measure. If her ESTA application had been denied, she would not have been able to travel and would have to apply for a visa at a US embassy. The pre-board checks for ESTA were performed electronically. I believe there's also a state where an application has to be reviewed, and that can take days to reach a decision. I don't know anyone who has had that happen though.