"I have no data yet. It is a capital mistake to theorize before
one has data. Insensibly one begins to twist facts to suit
theories, instead of theories to suit facts.
- - Sherlock Holmes in “A Scandal in Bohemia”, by Sir Arthur Conan Doyle

We don't have the facts yet.

But, I was working on something else today and the following popped up: "The Normalcy Bias."
http://en.wikipedia.org/wiki/Normalcy_bias
A quote from the article "The assumption that is made in the case of the normalcy bias is that since a disaster never has occurred then it never will occur. It can result in the inability of people to cope with a disaster once it occurs. People with a normalcy bias have difficulties reacting to something they have not experienced before. People also tend to interpret warnings in the most optimistic way possible, seizing on any ambiguities to infer a less serious situation."

I have also heard something like this referred to as "get thereitis."

Pure unsubstantiated speculation: could she simply have thought "I've done this a 1000 time before---no problem."

A cautionary tale.

I do hope more facts come out, but we will never know what she was thinking.