You know the average American is incapable of saving even 5% of their income, right? That's why this is so unbelievable to some.
Lets distinguish "incapable of saving" from "unwilling to reduce consumption".
It's not like she said "I quit my job on a whim and am going to go travel through Europe for a year to find myself". She's clearly a talented person with a sought-after skill and she probably knows she'll be able to find another job, this one just wasn't working out.
"You know the average American..." - She's not an average American. She worked at Dropbox. She is a tech-industry professional that has worked at some highly successful companies for a number of years.