Monitoring the details and the work produced is also needed.
Auditors decide what work they think is necessary in order to render their opinion. Its our profession and only we are experts as to what the scope of our audit should be.
If we see a MATERIAL weakness in internal controls then we are obligated to pass that on preferably in writing.
Assuming material weaknesses were found, a company the size of Enron would have had a staff that would have followed it up and yes, she would be held responsible if that wasn't followed up. Mostly large accouting firms turn any follow up on stuff like this into a consulting engagement.
However, even a reportable weakness would not be all that big a deal because the auditors share concerns because if the weakness is too big they won't sign off on the statements.
If she has a